Lecture 21: Thinking

Question 1

Luria’s triangular model

Answer 1

• hierarchy sensory areas -progressively more complex, abstract
• integration in association areas
• back down through motor system
• peak of cognition at the top
• spatial organization makes sense

Question 2

Structure of the human neocortex

Answer 2

Question 3

Dorsal and ventral systems of the cerebral cortex

Answer 3

Question 4

Neurons in the inferotemporal cortex

Answer 4

In the monkey, respond selectively to particular shapes. Histograms of neuron firings APs as a function of time in response to diff shapes.

Question 5

Other interesting cells in the inferotemporal cortex

Answer 5

Of monkeys and humans - neurons that selectively respond to faces.

Question 6

Agnosias

Answer 6

Deficits in “knowing”, cognitive deficits related to temporal lesions.

Question 7

Object agnosias

Answer 7

where entire concepts like vegetables are wiped out and patients cannot recognise objects even thought they can describe how they look perfectly well.

Question 8

Object agnosia, attractors, and model of the world

Answer 8

When a patient with visual object agnosia is presented with drawings, the patient would be able to copy them but could not accurately identify the objects.
Either did not recognise it at all and couldn’t describe the object or would describe it as something else - like a bird being described as a beach stump.
Holding onto the concept/idea of the dog - attractor. Using that to explain other concepts.

Building model of the world and making facts match the model of the world. Sometimes we change the model according to the facts, very often we change the world according to our model.

Fitting this visual input that I’m getting to something that is in my model of the world, even if I have to twist it a little to make it work. Probably doing this continuously. In order to make sense of this architecture of the mind we have - probably in the temporal lobe.

Although the idea of the train is lost, kept the concept that trains pull things; lurking in the background; trying to fit that in this picture.

Question 9

What injury results in visual object agnosia

Answer 9

Injury to a medioventral region of temporal cortex.

Question 10

Other types of aphasia

Answer 10

Broca’s, Wernicke’s, conduction, global. Different kinds of speech aphasia. Result of lesions in temporal lobe.
If the lesion is rostral - like wernicke’s area of the temporal lobe, then people have aphasias (lack of speech; different types - like motor aphasia or sensory/perceptual aphasia). Concepts are there, but not a natural flow of speech following grammar or logic. Can have speech lesion.

Question 11

Recordings from posterior parietal cortex in monkey

Answer 11

Monkey looks at screen and gets a reward if it does want we want it to do. Must signal if seeing something in two conditions: with juice and without juice. Monkey is very attentive if getting juice - trying to test the role of attention.

Response of the same exact neruon when the animal is trained to attend to the target or to ignore the target. The only difference is that sometimes he is rewarded.
AP as fcn of time; big difference in activity in the same neuron when the monkey is attending to the target or ignoring the target.

Question 12

Selective activation of neurons in the monkey parietal cortex - implication?

Answer 12

Neurons in Parietal cortex code for attention.

When we pay attention, we focus on a particular stimulus
and it becomes more salient in our experience.

One of the things going on in the parietal cortex is “attention”.

Question 13

What happens if there are lesions in the parietal cortex?

Answer 13

Patient has hemineglect.
Strokes normally happen in only one hemisphere. Many of the stroke patients have stroke in one parietal lobe, and these patients ignore the opposite side of the body/world. They neglect half of the world.

Question 14

Selective neglect of space following injury to the right posterior parietal cortex

Answer 14

Patient has been tasked to cross the dots in the drawing. Patient only did so on the right side of the drawing. Even though you ask him to cross every single dot, only crosses the dots on the right; can see it but ignores it — as though it’s not there.
This happens even though the patient can accurately report the shape - so seeing it but ignoring it.

See this also in drawings of clocks, houses, flowers; completely ignoring the left side of the image; unilateral visual neglect.

Question 15

Self-portrait by an artist following damage to his right posterior parietal cortex

Answer 15

Painter that painted his self portrait after the stroke.
Painted months apart, right after he had a stroke (top left); parts of the right
side of his face but everything else gone. As he is slowly recovering, maybe because
other cortical areas take over or neurons survived, the left part of his face
reappears.

Question 16

What do the patients with damage to their right posterior parietal cortexes tell us about the role of parietal cortex, dorsal stream, brain in general?

Answer 16

These three patients illustrates one of the syndromes that happen if you lose your parietal association, have damage to the parietal cortex.
Dorsal stream having an attention map of the world. Dorsal info coming from visual
cortex - physical map of the world; maps also coming from sensory cortex; which
not only represent the body and the world, but there are a couple maps that represent our attention —> way to zoom in and out of the picture.

Question 17

Thalamus as the site of attention - searchlight hypothesis

Answer 17

The thalamus might be the site of attention. The thalamus is connected to all the cortical areas; the thalamus is like grand central station where cortical info goes in and out; shortcut to the cortex via the thalamus.
Impossible to disentangle the thalamus from the cortex = thalamal-cortical circuit as a unit.

Crick interested in attention, wanted to come up with ideas of how we direct this searchlight of attention around in our minds. Directing your visual, auditory system light a searchlight on different stimuli - the thalamus is that searchlight. The light only points at one thing at a time. Cannot attend to more than one thing at a time. With thalamus, can serially attend to one thing at a time.

Question 18

what indicators are there that the thalamus might be the site of a attention

Answer 18

Thalamal circuits are hyperactive when paying attention to something. Parietal neurons responding strongly could be doing so because the thalamal inputs are strong.

One of the ways you go into coma is with thalamic lesions -attention is an emerging property generated by diff cofrtical areas, mostly in the parietal lobe but also areas of the frontal lobe associated with hemineglect syndrome. Thalamus could be part of that network as well.

Question 19

How do emotional and cognitive processes in the prefrontal Cortex exert control over behaviour

Answer 19

Through a pathway that begins in the orbitofrontal-ventromedial prefrontal cortex (OF) and from there projects to the dorsolateral prefrontal cortex (DLPFC), the premotor cortex (PM), and finally the primary motor cortex (M1).

Question 20

The size of the cerebral cortex and prefrontal cortex in mammals

Answer 20

Can plot.
Part of the frontal cortex called prefrontal cortex, which occupies almost a third of the entire cortical map in humans. Found a bit in mice and rats and smaller monkeys. Illustrated when looking at area of prefrontal cortex as a function of volume of the whole cortex (C). We are alone - we have the largest size and proportion of the prefrontal cortex.

Question 21

What is the significance of humans having the biggest proportion and size of the prefrontal cortex out of all mammals?

Answer 21

likely that whatever is going on in the prefrontal cortex is what makes us more different than other animals, is what makes us human.

Question 22

What are the major brain regions involved in thinking, planning, and deciding

Answer 22

Dorsolateral prefrontal cortex, ventrolateral prefrontal cortex, insular cortex, dorsomedial prefrontal cortex, orbitofrontal cortex, dorsal anterior cingulate cortex, posterior cingulate cortex, ventromedial prefrontal cortex, pallidum and striatum, premotor cortex.

Question 23

Orbitofrontal cortex and ventromedial prefrontal cortex

Answer 23

Associated with judgments called value. One simple way to unerstand behaviour
is that it’s like a carrot on a stick; we do this we like and avoid what we dislike.
And this is done by the assigning of value due to dopamine.

Question 24

Dopamine and orbitofrontal cortex and ventromedial prefrontal cortex

Answer 24

Dopamine signal when reward is predicted. Looked at it in the striatum.
But dopamine goes throughout the cortex and in particular in the ventromedial
and orbitofrontal cortex —> hotbed of domapine in the brain.

Question 25

Monkeys and reward prediction experiment - raisin and apple

Answer 25

First, give choice between raisin and apple; recording from neuron in the orbitofrontal cortex;
Frequency of APs as fcn of time. Show the monkey the image and the
monkey will choose what he wants. Monkeys love raisins. Neuron is super
happy when you show the monkey a raising. Same neuron when you show
the monkey an apple does not fire much.

A bit later, the monkey has to choose between an apple and a cabbage;
monkeys hate cabbage; the same neuron that use to fire for raisins and not
for apples; now the neuron is firing for apple not cabbage.
This neuron has switched its receptive field and now firing for the apple.

Question 26

Raisin and apple experiment implication

Answer 26

Neurons in the orbitofrontal cortex of a monkey signal the subjective value of an expected reward. This means that the neuron is coding for the preferred stimulus; the preferred food morsel.
More sophisticated than coding for things - coding for the value of things.

Question 27

Orbitofrontal cortex in human fMRIs

Answer 27

this area lights up when humans have to make judgements of value.

Question 28

Dorsolateral prefrontal cortex

Answer 28

Now looking at dorsolateral. Where neurons are keeping

facts about the world and making comparisons.

Question 29

Oribtofrontal cortex and dorsolateral prefrontal cortex and dorsal/ventral pathways

Answer 29

All this info as judging the value and trying to predict the value - more abstract.
Dorsal and ventral pathway not just representing the world and attention, but
trying to make a prediction about the world and prediction our attention.

Question 30

Measuring neurons in dorsolateral prefrontal cortex while monkey having to remember in which box the food morsel is.

Answer 30

Show the monkey food morsel. Close the carton. Lift it; And the monkey has to remember the food was on the right.

If you record from a neuron in the dorsolateral part of the prefrontal cortex; Can see how the activity of the neuron runs up with the delay.
The minute the monkey chooses the right box, the neuron returns to baseline; a temporary buffer of info. These neurons don’t fire above baseline if the monkey wasn’t shown the stimulus.

Single neuron recording, imaging that there are attractors of these neurons coding for different things; can imagine that you can then use
these attractors and compare against each other and see which is associated with a prediction of reward and that’s how you can make a decision.

Question 31

Dorsolateral cortex and the card sorting experiment

Answer 31

Dorsolateral cortex lights up when the person performs a task according to particular rules. You can change the rule by which the cards are sorted. Game in which you have to guess what the rules of the game are - the dorsolateral prefrontal
cortex lights up.

Not just simple comparison between things - you are really choosing different
future paths - will I follow this rule or that rule? Comparing strategies, not just
objects;

Question 32

size of dorsolateral prefrontal cortex in humans in relation to findings on dorsolateral prefrontal cortex

Answer 32

Comparing strategies, not just objects; how human may have the flexible minds that enable us to change our behaviour, because we have gigantic dorsolateral prefrontal cortex and continuously comparing behavioural strategies not just different objects. Continuously doing these calculations in our minds for things and for entire behaviours. Flexibility ingrained in our dorsolateral cortex, probably.

Question 33

Dorsal anterior cingulate

Answer 33

Our inner critic. Lights up when there is something wrong.

Question 34

Stroop task and the anterior cingulate cortex

Answer 34

Present to the person an image like letters that say blue;
present same letters in neutral colour (meaning doesn’t
respond to colour).

If you look at a card that says yellow but colour is green, anterior
cingulate lights up.

Question 35

Stroop effect and anterior cingulate cortex - implication

Answer 35

When info doesn’t make sense, is incongruate, this area lights up.
Keeping model of the world, and when seeing something that doesn’t
fit our model fo the world, it gets engaged.

Conflicting info - this part of the brain lights up. Role of the anterior cingulate cortex as monitoring.

Question 36

Phineas gage and ventrolateral prefrontal cortex

Answer 36

Gage - working the railroad; blasting rocks. When he was pushing in the dynamite to the bottom; the spark from the rock lit up the dynamic; shaft came through his brain; went thru his eye and into his prefrontal cortex. Survived; after a few months/couple of years, recovered. But massive change in his personality. Became completely disinhibited, had no self-control, very jocular. Had no sense of responsibility. Essentially lost his maturity. Prefrontal cortex last part of the cortex to go thru the critical period.

Question 37

Damage to the ventrolateral prefrontal cortex

Answer 37

Damage to Ventro lateral PFC - abolished self control.

Question 38

Ventrolateral PFC and OCD, depression, Tourette’s

Answer 38

Very active in patients with depression, with OCD.

Question 39

What are some things that cause the insular cortex to light up

Answer 39

Emotions, love, sex, care; seems related to addiction

Question 40

Insular damage and addiction

Answer 40

Damage associated with an improved ability to quit smoking.

One study - the patients are trying to quit smoking - addiction. Scanned patients during the trial for quitting smoking;
Found that some did quit and others didn’t; and in some people was associated with complete break with addition and other with some addiction left; saw differential activation of the insular cortex in these patients when they imaged; more active in the patients successfully quitting, coming out of addiction. Goes in the direction that there is a correlation with the activity of the insular cortex and terminating addicting behaviour.

Question 41

default mode and the posterior cingulate cortex

Answer 41

If you scan the brain of people with fMRI; when person doing nothing,
the brain is still active. Never a time when the brain is not active.
If you scan patients that are idling, their brain activity in particular areas, coordinated in whole network - default-mode network.
The activity of the brain when you are not doing anything. The centre of this default mode network is the posterior cingulate.
The network stretches through the entire cortex and changes in time, very low frequency oscillation, and we don’t know what it does. ==> distributed network.

Question 42

What is one idea surrounding the default mode network

Answer 42

People have argued that maybe this default mode network is the self. When thinking of yourself, that is the self.

Question 43

Activity of posterior cingulate and neurological disorders

Answer 43

Correlation between activity of the posterior cingulate and default mode network that affect the concept of the self - schizophrenia, autism, Alzheimer’s. Not causation. But intriguing that maybe part of what’s going on in the prefrontal cortex is the generation of the concept of self, which happens in the central hub of the posterior cingulate.

Question 44

Consciousness

Answer 44

Argue that it’s the most sophisticated thing that our brain does. We are conscious, aware of ourselves; difficult to pin down; related to our self-awareness, aware of the world and our selves; subjective feeling, comes from the inside; associated with unity, we are one. Why are you one and not two people? Brain thinks that we are one. Something global and something unique. Associated with intentionality.
Could be like a loop – first aware of something and then yourself.

Question 45

Different ideas about consciousness

Answer 45

1. unconscious processing (Helmholtz, Freud).
2. readiness potential before awareness (Libet).
   3, Just outcome of brain function (Dennet - what we can consciousness is a result of all of our brain activity; try to capture all of that and label is consciousness. No such thing as unique thing called consciousness.)
3. discrete state (Koch, Crick)
4. off limits to human intelligence (McGinn)
5. Accesible but too complex (Searle, Nagel) - emergent, not reductionistic.

Question 46

Idea of consciousness as discrete state

Answer 46

Believe generated actively; postulated that claustrum in forebrain that connects to the cortex - whoever is doing consciousness in the brain must be connected to everyone else; must broadcast that info that you are one
everywhere; claustrum connects to many parts of the cortex. Also, attention in the thalamus - could also be generating consciousness. If experience is conscious, going to the thalamus.

Crick, Koch

Question 47

Idea of consciousness as an emergent property

Answer 47

Searle, Nagel.
An emergent property; like magnetism. If you’ve got individual atoms, not magnetic, but a bunch of atoms = magnetic. Consciousness is the emergent property of the activity of many neurons. As you climb up the ladder, get and more emergent properties.

Question 48

Deheane and consciousness as emergent property

Answer 48

Deheane. Used fMRI scans and mapped cortical activity. Subjects volunteered to be subjected to stimuli that were subliminal - so brief that you don’t perceive it. For visual stimulation, anything faster than 30HZ cannot be perceived by most people; why movie pictures shot at 30Hz. When he gave the subject subliminal stimuli, visual or auditory, and scanned the brain, still see that the primary visual and primary auditory cortex lit up - stimulus getting to the cortex, but person is not conscious of this. Lighting up only the primary sensory areas. If you make the stimuli slower, and scan patients - suddenly, the entire cortex lit up, and activity flowing all over the cortical map, not just the primary sensory areas. Proposed theory - global workspace theory for consciousness. Idea is that consciousness is an emergent property that occurs in our brain when everything gets connected together. A lot fo the connections are excitatory; if stimulus is long enough, trips the ventral stream and everything get’s activated - that’s when you are conscious of the stimulus.