Neurobiology of the three hypotheses
Notes…
Connectionism
A
considerable amount of work has been done in creating and training neural nets
to effect recognition of features in the net’s environment. Nodes are connected
in various ways, with the flow of information shown by arrows (see fig 2.12
below). Nodes have two characteristics which can be altered, or ‘trained’ – how
much input they need in order to fire to the next level – and how much they
‘listen’ to each of the nodes in the layer below. The connection may also be
either inhibitory (input from a lower node reduces the chance the recipient
will fire), or excitatory (increasing the chance it will fire).
Interesting
parallels emerge to the functioning of neurons in the brain. In ‘Rethinking
Innateness’, Elman, Bates, Johnson,Karmiloff-Smith, Parisi, and Plunkett, MIT
Press, 1999:
“One
form of training involves what is called “auto-association.” In this task, a
network is given an input and is trained to reproduce the same input pattern on
the output layer. What makes this a non-trivial problem is that such networks
(such as the one shown in Figure 2.12) contain a narrow waist in the middle.
This means that the network is forced to find a lower dimensional
representation
of the inputs. Often these internal representations capture interesting
features of the inputs. For example, Elman and Zipser (1988) trained
autoassociators to reproduce speech sounds, and found that hidden units [such
as the ‘waist’ units here] learned to respond to different classes of sounds
(e.g. vowels, consonants, and certain stops). This form of training also
addresses the question of where the teacher comes from, since in auto
association, the teacher is nothing more than the input itself. “
A
similar system could thus emerge naturally in the pattern recognition centres
of the brain, where the ‘waist’ neurons correspond to sentic, explorer, or
quest archetypes. Output from these archetype neurons would then feed to
emotional and prefrontal cortex areas, which, based on current attention
patterns, would then initiate the next action. Archetypal features not
recognised by the hard wiring of the retina have thus a mechanism for
emergence.
An
example of how features can combine to identify objects is shown in the
following diagram, also from the above mentioned book, on how a neural net was
trained to recognise words:
Recognition
(Rita
Carter ‘Mapping the Mind’ Phoenix 2000 p180-200)
“There
are two distinct types of recognition: one is the inner ‘ah-ha!’, a cerebral
snap of the fingers that happens when you hear a familiar piece of music or see
someone you know. Getting a joke is a form of this type of recognition – a good
punchline delivers a sudden jolt of recognition. So is coming up with a
solution to some problem that you just ‘know’ is right. The penny drops. Got
it. Eureka!”
This
type of recognition is quite different from the other – the conscious
acknowledgement of a correct answer that you arrive at if, say, you add a
string of figures together…But…everyone has to arrive at this sort of knowing
by a conscious effort. Automatic recognition, by contrast, is instant,
effortless and unavoidable.”
Here
Rita introduces the idea of cerebral and limbic/emotional recognition
processes, then continues by showing what happens if the two pathways stop
working smoothly together, as in Fregoli’s Delusion, and Capgras Delusion.
However, this explanation is limited by the idea mingling here and there in
this passage that cerebral processing needs to be conscious, and deliberate, while
emotional recognition needs to be sudden. The emotional feeling of surprise can
accompany either process, but is presumably subsequent to them also – a
separate issue. Not ‘emotionally’ recognising a family member as who they
physically appear to be, via the conscious route, or ‘emotionally’ recognising
people who actually bear no resemblance to the person you think they ‘really’
are do not necessarily require surprise, or the ‘aha’ moment. The problem seems
to be that they are for some reason triggering the ‘imposter’ emotion. That
conflicting reports are coming by different pathways.
Face recognition
As
we have noted, new born infants identify faces as three high contrast blobs,
and they prefer this stimulus to mothers such as a black face shape, or faces
where the elements (nose, eyes, mouth) have been shuffled. Infants do not
prefer a fully featured face until the age of around two months, when a new
archetype emerges. Johnson suggests that the initial archetype is recognised
with the involvement of the colliculus and the pulvinar section of the
thalamus. (Johnson MH, The Cognitive Neuroscience of Development, Oxford
University Press, 1990). New born infants are also able to tell the difference
between straight and curved lines.
The
later preference for fully featured faces is apparently learned. Scientists
have identified neurons in the brains of mammals (DI Perrett, ET Rolls, and W
Caan, Visual neurones responsive to faces in the monkey temporal cortex,
Experimental Brain Research, 47(3), 329-342, 1982), and have shown that sheep
raised with horned companions develop horn identifying cells, while those
raised with companions without horns do not. (KM Kendrick and BA Baldwin, Science, 236, p448-50)
Superior and Inferior Colliculus
For those interested
in the brain structures involved in this process, the essentic form is probably
detected by pattern recognition structures in the retina, and passed direct to
the superior colliculus without any conscious involvement or awareness at this
stage. The superior colliculus activates reflexes turning the head and eye so
that the most sensitive part of the retina, the fovea, can analyse the
stimulus, whether the pupil of a threatening eye, or the sharp end of a spike.
At the same time, information is also sent down a nerve bundle from the retina
to the thalamus, where the shape is relayed to other centres (amygdala etc) to
initiate the appropriate emotional response; and to the visual cortex, for
recognising the object, and determining its location relative to its
surroundings. Information also goes to the ascending reticular activating
formation, which participates in bringing relevant aspects of the stimulus into
consciousness, and then modifying the initial emotional response.
It is not known
whether other sentic forms are similarly recognised at the retinal stage, in
the superior colliculus, or elsewhere, but it is believed that the inferior
colliculus, which handles auditory stimuli, recognises sentic forms from
auditory sources, and initiates appropriate instinctive behaviour.
Catherine Carr in
her lectures refers to the work of JH Casseday and E Covey:
“A neuroethological theory is
proposed that accounts for a large and diverse body of evidence. Although aimed
at characterizing the inferior colliculus in mammals, the theory also applies
generally to the auditory midbrain in vertebrates. The theory has two
hypotheses:
- Tuning processes, in the inferior colliculus are related
to the biological importance of sounds.
- There is a change in timing properties at the inferior
colliculus, from rapid input to slowed output; this transformation is
related to the timing of specific behaviors.
Expressed in neuroethological
terms, at least some neurons in the inferior colliculus are tuned to
sign-stimuli (behaviorally relevant stimuli that trigger species specific
behavior), and the processing of these sign stimuli triggers fixed action
patterns for hunting, escape or vocal communication. The resulting temporal
transformation adjusts the pace of sensory input to the pace of behavior.
Evidence for the theory comes from anatomical, neurophysiological and
behavioral studies and includes:
- massive convergence of parallel auditory pathways at the
inferior colliculus
- interaction of the inferior colliculus with motor systems
- tuning of auditory midbrain neurons to biologically
important sounds
- the slow pace of neural processing at the inferior
colliculus
- the slow pace of motor output.
The
theory has the following implications. Neurons in the inferior colliculus are
filters for sounds that require immediate action, such as certain sounds made
by prey, predators or conspecifics. Neural processing in the inferior
colliculus is species specific, resulting in filtering for these kinds of
sounds. Specific action patterns should be correlated with the activity of
neurons in the inferior colliculus. Motor activates may modify neural
processing in inferior colliculus neurons. The rate at which information is
transmitted to the thalamus is regulated by the inferior colliculus.” (http://www.glue.umd.edu/~carr/Hearing/lecture9.html)
Right versus Left
(Rita
Carter ‘Mapping the Mind’ Phoenix 2000 p183)
“Both
hemispheres have a distinct role in sound processing, and this means that
sounds are dealt with (and therefore experienced) slightly differently
according to which ear they enter. For example a person deaf in the left ear
will receive most sound signals in the left auditory cortex (the side of the
brain opposite the ‘good’ ear). This is the side that deals mainly with the
identification and naming of sounds rather than their musical quality, so
rhythm and melody perception may be blunted.” [And hence emotional
interpretation?]
“Conversely
a person deaf in the right ear may find that words are more difficult to
distinguish than music, irrespective of the loudness.” [And the prosody and
hence emotional content of the words easier?]
Location of joy and reverence archetype receptors
(Rita
Carter ‘Mapping the Mind’ Phoenix 2000 p208)
Stimulation
in the temporal/limbic region ‘may produce intense feelings of joy, and a
feeling of being in the presence of God. Religious visions may occur’.
Location of fear and anger archetype receptors
(Rita
Carter ‘Mapping the Mind’ Phoenix 2000 p135)
“Expressions
of fear are picked up and identified by the amygdala – a tiny piece of tissue
in the unconscious limbic area of the brain. One part of the amygdala responds
to facial expression and another is sensitive to tonal qualities in the voice –
the give-away rasp of anger or quiver of fear. The left amygdala seems to
respond more to vocal expression while the right amygdala is more sensitive to
facial movement.”
(Rita
Carter ‘Mapping the Mind’ Phoenix 2000 p142-4)
“The
amygdala…is the brain’s alarm system – the central generator of states of mind
that evolved to aid survival under threat. Stimulate one part of the amygdala
and you get the typical fear reaction – a feeling of panic combined with
flight. Stimulate another and you produce what people have described as a
‘warm, floaty feeling’ aqnd excessively friendly behaviour – appeasement.
Activity in a third region of the amygdala results in outbursts of rage.”
“The
amygdala receives emotional stimuli first via what Joseph LeDoux has termed
‘the quick and dirty route’: a fast track that produces an almost instantaneous
automatic response – smile, jump back or lunge forward. A quarter of a second
later, however, the information reaches the frontal cortex where it is placed
in context and a rational plan of action is conceived to cope with it.”
“Brain
scans of psychopaths by Professor Robert Hare at the University of British
Columbia suggest their behaviour may be partly due to an amygdala malfunction,
particularly in the right hemisphere. A normal amygdala is activated by
emotional stimuli. Psychopath’s amygdala show little response at the sight of
another’s distress. Some studies show they do not react to threat stimuli
either. Scans show that psychopaths process emotional information unusually: in
most people the right hemisphere lights up most in an emotional situation, but
psychopaths brains are equally active in both hemispheres.
“The
inability to sense emotion in others and to generate it themselves leaves
psychopaths immune to remorse and punishment. Some think that this is due to
brain damage; others that lack of maternal bonding may be responsible: close
interaction between infants and mothers is necessary to stimulate and maintain
normal function in the amygdala.”
Location of disgust archetype receptors
(Rita
Carter ‘Mapping the Mind’ Phoenix 2000 p135)
“Disgust
– which means, literally ‘bad taste’ – is expressed in the face by a
distinctive wrinkling of the nose, narrowing of the eyes and pursing of the
lips. Brain scans show that watching a person displaying this expression
activates the anterior insular cortex – an area of brain that is also
stimulated by offensive tastes. The sight of an expression of intense disgust
also lights up a circuit in the observer’s brain that connects the cortex with
the limbic system.”
“Certain
physical gestures – the Gallic shrug of contempt, the thrust out pelvis
signifying aggression, the drooping shoulders of resignation – seem to be
processed by the brain in a similar way to facial and tonal expressions…”
‘Hey – something is wrong…’
(Rita
Carter ‘Mapping the Mind’ Phoenix 2000)
“The
caudate nucleus is the part of the brain that automatically prompts you to wash
when you are dirty; that reminds you to check the doors before you leave the house;
and that alerts you to and focuses your attention on anything that is out of
order.
“It
does this by activating one particular area of the frontal lobe – a spot in the
orbital cortex*, the area of the frontal lobe just above the eyes. This is the
area that lights up when something unexpected happens…
“It
was first identified during monkey studies done by Professor E. T. Rolls at
Oxford University. The animals were shown green and blue lights and trained to
associate the blue light with a reward of fruit juice, and the green light with
a salt drink. Once they had grasped the link between blue=juice and green=salt
the drinks were switched. Suddenly the monkeys got a salt drink when they saw
the blue light. When this happened an area of the brain that had been quiet
until then leapt into life. The neurons in the orbital complex that lit up were
not simply responding to the saltiness of the drink – taste discrimination and
the simple “ugh!” reaction happen elsewhere in the brain. This particular area
was clearly activated by the discovery that something in the world was not
quite right…
“Since
then brain scans on humans have shown that this area is particularly lively in
people with OCD [obsessive-compulsive disorder]. When a person with a
handwashing compulsion is told to imagine themselves in some filthy place their
caudate nucleus and orbital fontal cortex fire away like mad.”
*concerned
with higher order planning of action
Three Subnetworks of the Human Attention System
(Catherine
Harman and Nathan A Fox, in Development of the Prefrontal Cortex, Evolution,
Neurobiology, and Behaviour, Paul H Brookes, 1997)
“Posner
and Peterson (1990) delineated three subnetworks of the human attention network
using a variety of methodologies, primarily PET. These three subsystems are an
anterior attention subnetwork, a posterior attention subnetwork, and a
vigilance subnetwork. …
“Posterior
Subnetwork: Neural Bases and Function The neural substrates of the
posterior attention subnetwork include the parietal lobes, the superior
coilliculus, and the thalamus – more specifically the pulvinar nucleus of the
thalamus. This system functions to enhance the sensory processing of stimuli at
particular locations, operating in conjunction with mechanisms that control the
orienting of sensory organs. Once a particular location is selected, the
sensory organs are oriented to it, and the attributes of stimuli from that
location are enhanced. Thus the posterior attention subnetwork operates
exclusively on external or environmental information.
…The
elaboration of stimuli at a particular location involves three component
processes 1) maintaining engagement at a particular location, 2) disengagement
from that location upon selection of another location, and 3) the actual
shifting of the index of attention from one location to another. Maintaining
engagement at a particular location is primarily subserved by the parietal
lobes. Disengagement is primarily subserved by the pulvinar nuclei of the
thalamus, and the superior colliculus shifts the index of attentional focus
from one location to another.
Anterior Subnetwork: Neural Bases and Function The neural substrates of the anterior attention subnetwork
include regions of the frontal lobes and anterior regions of the paralimbic
cortex, most notably the right dorsolateral prefrontal cortex and the anterior
cingulated gyrus. The anterior cingulated is a major output of the limbic
system, suggesting an important role for this structure in influencing
emotional experience and expression. It has long been recognised that the
limbic system, particularly the amygdala, is crucial to emotional processes. At
least one function of the anterior attention subnetwork is to detect target
information, that is, to match the representation of a goal state, or a desired
state, to a current state or sensory input. Unlike the posterior attention
subnetwork, which primarily enhances the processing of stimuli fom external
environment, the anterior attention subnetwork utilises interior data from
memory storage in addition to current input from sensory processing systems. …
Its role in consciousness may be to carry a model of the state of the world and
to detect deviations [and matches?] from those expectations.
Vigilance Subnetwork: Neural Bases and Function Finally the vigilance subnetwork has been identified as being
involved in maintaining the alert state over substantial durations, on the
order of seconds and minutes, in contrast to milliseconds. The neural
substrates of this subnetwork include the brainstem area known as the locus
ceruleus (LC) and the cortex of the right frontal lobe, with the LC supplying
norepinephrine to the right frontal cortex. In the emotional domain, LC cells
are particularly responsive to threatening or aversive stimuli, suggesting an
important role for this system in the fear state…”
Subnetwork Interaction Although the subnetworks are distinct,
certainly they interact. … Typically the anterior attention subsystem selects
targets based on schema stored in the semantic network, passing control to the
posterior attention subnetwork when attention to the environment is required. …
When vigilance subnetwork activity increases, anterior attention network
activity decreases and posterior attention network activity increases. The
decrease in anterior attention subnetwork activity likely corresponds to the
clearing of conscious awareness in order to speed detection and responding to
particular targets. The posterior attention subnetwork activation likely
corresponds to enhancing data processing of environmental stimuli in order to
speed target detection.
Prefrontal Cortex
All mammals
(including echinoderms and placentals) have regions of prefrontal cortex, and
it is assumed therefore that this brain region was present in their triconodont
ancestors. Other creatures do not have cerebral cortex, but birds do have brain
regions homologous and perhaps
functionally analogous to the pfc of mammals.
In his book ‘Going
Inside’ (Faber and Faber, 1999, pages 200-202), John McCrone explains what is known
of the neurobiology of pfc processes:
“There is an
elegance to the brain’s design. Sensation flows in and condenses to produce a
focus. Then, this focus becomes the spark for a wave of activation which floods
back down the hierarchy to create a spread of motor plans and sensory
expectations…
The part of the
brain that seems to be responsible for turning the actual flow of processing
around – the place where the escalated residue of each moment’s processing
becomes explicitly mapped – is the prefrontal cortex….At one stage, it was
believed that it might have no particular structure at all. But it has since
become clear that the prefrontal cortex is probably split into at least six
major processing regions…”
Regions are orbital
(underneath the prefrontal lobe); medial (inside – either side of the main
cleft separating the two hemispheres); lateral (at the two outer sides of the
brain); dorso-lateral (the upper part of the outer side); and ventro-lateral
(the lower part of the outer side).
Orbital Prefrontal Cortex
In
‘The Prefrontal Cortex’ (Fuster, 3rd edition), the Orbital PFC
(underneath the frontal lobes) is identified as the region responsible for the
initiation and integration of emotional behaviour, transmitting to the dorsal
cortex information from the limbic system on the internal milieux and its
needs, and is a major site of emotional memory. It plays a role in controlling
sensory attention, in that it inhibits possible distractions from inside or
outside, including instinctual and emotional behaviour.
Intriguing
evidence for instinctive reaction to shapes is revealed by damage to this area.
Patients often cannot stop their hands from reaching out and using tools and
objects simply because they are ‘there’, in front of them.
The
orbital area sends messages to the hypothalamus to control eating and
aggressive behaviour. It also plays an important part in directing eye
movement, and upper limb activity. It has a high concentration of
reward-related cells, and is directly connected with the medial thalamus
(mediodorsal nuclei), hypothalamus, ventromedial caudate, and (especially) the
amygdala. Damage to this area results in distractibility, instinctual
disinhibition, hypermotility, euphoria, mindless repetition of tasks and
activities, irritability, and lack of moral restraint.
[The
connection with the limbic system is largely through the anterior cingulate
gyrus, which seems key to feeling and expressing emotion. It links to the
sympathetic and parasympathetic nervous systems, and visceral sensory
afferents.]
Dorsal prefrontal cortex
The upper flank
– referred to as the dorsal prefrontal
cortex receives the location and motion mapping stream from the parietal
cortex, and it thinks about place. McCrone goes on:
“…it seems that
some parts of the DPFC focus attention on points in the real space about us
while others help us navigate our way around an associative space, steering us
through a mental space containing thoughts and meanings.”
In other words, the
dorsal prefrontal complex is the probable location of the agent containing the
elements of the explorer hypothesis.
While the Orbital
(and Medial) PFC tells what needs the organism has, and prevents it from paying
attention to irrelevant stimuli, the Dorsolateral PFC selects what we SHOULD
pay attention to (including memories), in order to take action to achieve the
ends given it. While the orbital PFC has lots of reward-based cells, the Dorsal
PFC has lots of delay-activated cells. It is the main site for working memory,
and for making and executing plans. It is directly connected to the lateral
thalamus, dorsal caudate nucleus, the superior temporal and intraparietal
sulci, and (especially) the memory related hippocampus and parahippocampal
cortex. Damage results in a lack of movement, planning, apathy, depression, and
blunted emotional expression and communication. (Fuster, p.101, 147, 182-3)
In the sensory
cortex, where incoming sensory information is processed to reveal its basic
qualities, we see a fundamental division into two major areas. One concentrates
on where things are, and how they are moving. The other focuses on what
the object is. And the prefrontal cortex, where all this information is turned
into what to do next, has the same split.
Ventromedial Prefrontal Cortex
The lower part of
the prefrontal lobe, though, referred to as the ventromedial region, takes the
object identity stream from the temporal lobe, and according to McCrone, it
thinks about people, things and events:
“There is evidence
that we use the ventromedial to think about complex social situations –
thoughts about whether people really mean what they say, or how to turn some
difficulty to our advantage”
In other words, the
ventromedial complex is the probable location of the agent containing the
elements of the sentic and quest hypothesis.
In short:
“the prefrontal cortex takes the core of the
moment apart to see it in terms of its eating, manipulating, associating,
socialising, and orienting possibilities… it should give an idea of why each
moment of consciousness is flavoured not just with a sense of understanding,
but also intention… guiding the consequent wave of output”
On p209, McCrone
refers to experiments in which electrodes were inserted in the prefrontal
cortex to see how cells there behaved while cells in the temporal lobe were
registering the sensation of an image of a boat. Prefrontal cells mapped the
fact that the temporal lobe was ‘seeing’ this, but when the image was removed,
or substituted with something else, if the monkey had a reason to keep the
image of the boat ticking over in ‘working memory’ to come back to it later –
to match to a later image for a reward – then the cells in the prefrontal
cortex continued firing away while those in the temporal lobe stopped. This was
then confirmed in f-MRI scans on a human subject in 1995, when the prefrontal
cortex was found to keep the gist of an idea ticking over for days, while the
sensory areas of the brain had long since stopped their associated firing.
“It was clear from
such experiments that the prefrontal cortex was essential for forming states of
intention, and could maintain them for a short time. However, its grip on a
memory state was extremely fragile; better than the temporal lobe, but still, a
major shift in attention would wipe even the prefrontal circuits clean,
preparing them to deal with a fresh event. The hippocampus was the brain’s real
memory trap, taking the snapshots that allowed moments to become permanently
woven into the fabric of the brain.”
Inferotemporal cortex
The Inferotemporal
cortex is part of the temporal lobe which specialises in object recognition and
memory associations. It is the step immediately prior to the area from which
information is sent to the prefrontal cortex, and it is to this prior area that
the prefrontal cortex (specifically the area around the sulcus principalis)
responds, presumably to enhance, inhibit, or fine tune information from that
visual area.
“After several
decades…more than thirty visual mapping areas were identified. At the top of
this hierarchy, cells appeared to code for actual objects – or at least
components of objects. The workings of one of these areas, the inferotemporal
(IT) cortex, was only unlocked by another famous experimental fluke. Like Hubel
and Wiesel, a group of researchers had been trying every kind of stimulus to
make an IT cell fire. Then, one of the scientists caught his hand in the
projector beam and the cell went wild. It seemed that the monkey’s brain had a
neuron whose sole job was to signal the presence of hand shapes within the
visual field.” (p.90)
Is the hand shape
perhaps that of the Fan?
“More careful
experiments had since proved that while some IT neurons were tuned to react to
highly specific phenomena like hands and faces, most coded in a more general way.
They did not code for specific experiences like grandmothers, but represented
the perceptual elements – the assortment of shapes and textures – that might be
needed to paint a population vote of a grandmother’s face. …
There were cells
that fired to T-shapes, stars, pairs of touching balls, and of course, other
common fragments of experience like hand shapes and face shapes. Other cells
seemed to specialise in coding for surface textures such as hairiness or
smoothness. The IT neurons were also topographically arranged so that
neighbouring cells had the same basic object preference, but with a slight
shift in orientation, size or proportion. For instance, within a group of cells
responsive to star-shaped patterns, some would fire at a peak rate to fat or
many armed stars, while others might prefer skinny or sparsely armed stars.”
(p150-1)
Thalamus
(Rita
Carter ‘Mapping the Mind’ Phoenix 2000 p150)
Everything
coming in through the senses goes first to the thalamus where it is sorted and
shunted onward to appropriate processing areas. In the case of emotional
stimuli – the sight of a snake in the grass for example – the information is
split in two and sent on its way via two separate pathways. Both paths end up
at the amygdala, the brain’s alarm system and generator of emotional responses.
The routes they take, however, are quite separate.”
“Pathway
number one goes to the visual cortex at the back of the brain which analyses it
and then sends on what it finds. At this stage it is just information – a long,
thin, wriggly thing with patterns on its back, here, now. Next the recognition
areas of the brain get to work on it, deciding what this long wriggly thing is.
The information, now tagged as a snake, triggers the release of stored
information about snakes – animal/different types/dangerous? – from long-term
memory. These elements are added together to create a message: ‘Snake! Here,
now, aargggh!’ (or something to that effect). This is then sent to the amygdala
where it stirs the body to action.
“As
you can see, pathway number one is a long and winding one with several stops
along the way. Given the urgency of the situation, on its own it would be
dangerously slow – a quick response system is needed. This is provided by the
second pathway to emerge from the thalamus. The thalamus is close to the
amygdala and is linked by a thick band of neuronal tissue. The amygdala in turn
is closely connected to the hypothalamus, which controls the body’s fight or
flight response. These connections form LeDoux’x ‘quick and dirty’ route along
which information can zap from eyes to body in milliseconds.”
McCrone:
“…researchers were
surprised to discover that the thalamus had a topographical organisation that
seemed precisely to mirror that of the cortex above. The bulk of the
connections with the prefrontal cortex were grouped together in a forward
section of the thalamus known as the medio-dorsal nucleus (MD). The various
levels of the motor cortex connected to a series of nuclei along the side of
the thalamus. The sensory hierarchy was then connected to the pulvinar, a large
nucleus taking up the whole back third of the thalamus. The divisions kept on
going with the pulvinar, for example, having at least four sub-regions. Some
anatomists even felt they could make out the match for individual cortex maps,
such as V4 or the IT area.” (McCrone p.221)
The cells of the
mediodorsal nuclei in primates consist of two types, relating to two areas –
magnocellular and parvocellular. The magnocellular ones connect mainly to the
orbital and medial prefrontal cortex, and the parvocellular to the mid and
frontal dorsolateral pfc. A third group (from the pars paralamellaris sector of
the thalamus) project to the posterior dorsolateral pfc. The mediodorsal part
of the thalamus has its major inputs from the amygdala, hypothalamus, and the
olfactory cortex.
Fuster (p22): “In
summary, the prefrontal cortex receives, directly or through the thalamus,
inputs from the hypothalamus, the subthalamus, the mesancephalon, and the
limbic system. The precise nature of these inputs is unknown, but may be
tentatively inferred from what is known about the structures of origin.
Influences from the hippocampus, in
particular, may be crucial for motor learning and memory, whereas the
inputs from the substantia nigra and some of the lower brain structures are
probably related to the execution of movement. Inputs from the mesancephalon,
the hypothalamus, and the amygdala are related to the internal state and
motivations of the organism. Inasmuch as some of these structures receive
information from sensory areas, it is possible that they pass on to the
prefrontal cortex information about the motivational significance of external
stimuli. Next, we shall see that the prefrontal cortex also receives sensory
information directly through neocortical pathways, although that information
may not deal so much with affective and motivational aspects of the environment
as with its cognitive aspects, that is perception and memory. “
These latter
sensory pathways remain separate (somatic, auditory, visual, gustatory, and
olfactory) at least until they arrive
in the prefrontal cortex. There they arrive in separate areas, but in the area
of the sulcus principalis and the ventral and medial areas of the pfc, bi and
trimodal connections are made, clearly providing cross modality association.
The other arrival sites are also seen to project to joint areas. And they
project in largest numbers to layer III of the six layers of the cortex.
Striving effects in Music etc
(Rita
Carter ‘Mapping the Mind’ Phoenix 2000 p244)
“Jaak Pranksepp
thinks the emotion-tugging effect of certain types of music lies in its
similarity to vocal (but not verbal) signals that carry emotional messages
between animals. The tension-building sequence with delayed resolution that
typically brings about the chilly spine feeling, for example, has features in
common with the sounds made by infants – both human and animal – when they are
parted from their mothers. In animals these cries have been found to trigger a
drop in oxytocin – the brain chemical most closely associated with parental
bonding – and they also bring about a drop in the mother’s body temperature.
When the mother is reunited with her baby, the child responds by ‘resolving’
the cry – a vocal performance not dissimilar to closing a phrase of music with
a satisfying final note. At the same time the mother’s oxytocin level goes up,
and her body becomes warmer. Women have been found to feel the tingle more
keenly than men, which fits in neatly with this theory.” (Jaak Panksepp is a
psychologist in Ohio.)
Final comment
You may have
noticed that one notable emotion has been ignored throughout this text. That of
disgust. But perhaps there are times when some things are better left hidden,
for the benefit that hiding them may convey. One would expect this emotion to
be displayed in shape and colour, and to evoke a standard, core consciousness
response. Fun for you to explore, if the Secret takes you. But I do have one
thing to say about disgust.
In thinking of many
of the experiments referred to above, experiments involving keeping monkeys in
confined and distressing conditions, implanting electrodes in their brains, and
severing one part of the brain from another to see what happens, associations
may form in one’s mind, as mine, of experiments conducted by Nazi scientists on
concentration camp victims.
While the skill of
the experiments and the value of the information extracted was doubtless far
greater with the use of monkeys, the insensitivity and disrespect for the
dignity and feelings of these fellow creatures seems little different. It is
very easy to contemplate the Nazis and feel disgust and disapproval for what
they did, less easy to recognise behaviours of our own that are equally
reprehensible. I think we have a responsibility to conduct ourselves better,
and to tackle that task.
We know that
monkeys do not have the extended consciousness we do. Would that justify us
doing these things to a young child, then? Equally we know that it is highly
likely that they have a similar core consciousness to us. We know for sure that
they feel what we do to them. We know they are social creatures, and we know
what it is to be deprived of that hug, or the affection of others of our
species. We know what it is to be lonely. We know for sure that they are not
automata.
Come on guys. Can
you go on allowing yourselves to be so consumed with the emotions that Secrets
prompt in you, can you can allow yourselves to commit such cruelty, just to see
round the next corner? Which part of the brain lights up when you load the next
consignment of people into a gas chamber is not information that is worth the
price. And nor is a lot of what is currently being done to fellow primates and
other feeling creatures. Step back for a moment from what you are doing, and
take a longer term view. Then clean up your act, so your kids do not have to
hang their heads in shame when your grandchildren ask what you did in life.