Problem 6 Flashcards
What is the fundamental assumption on the mind body problem ?
Mind + consciousness are functions of the brain
–> neuroscience tries to explain how the brain produces mental processes
ex.: perception, memory, language
The NS is divided into 2 main parts.
Name them.
- Central NS
- -> includes brain + spinal cord - Peripheral NS which carries info to + from CNS
The PNS includes the Somatic system and the Autonomic system.
Name their consecutive functions.
- SNS
- -> controls skeletal muscles + relays sensory messages about touch, pressure etc to CNS - ANS
- -> controls the glands + energy organs like heart, blood vessels etc
a) sympathetic
b) parasympathetic
The brain consists of 3 major divisions.
Name them.
- Central core (CC)
- -> oldest part consisting of
a) brain stem
b) cerebellum
c) thalamus + hyypothalamus
- Limbic system
- -> wraps around CC + includes
a) hippocampus
b) amygdala
- Cerebrum
- -> divided into 2 cerebral hemispheres + connected by corpus callosum
Name the most notable features of the cerebrum.
- Gyri
- -> ridges - Sulci
- -> valleys - Fissures
- -> deep valleys
Primary sensory areas
Do the first stages of analysis of incoming stimuli in the various sensory modalities
–> damage can lead to sensory loss
ex.: primary visual area, auditory area
Association cortices
Associate stimuli from various modalities with each other
–> are the cortical areas outside the primary sensory motor areas
Why is the left hemisphere said to be the dominant one ?
Is this even true ?
- Because, language and communication centers here + verbal thought seems to be so important for the control of voluntary action
- No, as under appropriate condition the right HP can take charge + perform tasks
BUT: right HP usually just helps the left one where it can or else remains passive
What is the function of the occipital lobes ?
Processing visual info
–> damage can lead to visual agnosia
What is the function of the parietal lobes ?
Recognition of objects for integration of info from different sensory modalities
What is the function of the frontal lobes ?
- Formulating plans for reaching goals
- Sequencing of actions
- Inhibiting inappropriate responses
–> higher order control
What is the function of the temporal lobes ?
Memory storage, by working in conjunction with limbic system structures
e.g.: episodic + semantic memory
The cortex is said to be organized according to the principle of contralateral organization.
What does this mean ?
The left hemisphere analyzes stimuli + controls actions of the right side of the body and vice versa
Commissural fibers connect the two hemispheres of the brain.
What will thus happen if these fibers are cut ?
Sensor inputs + thoughts cannot be transmitted directly from one hemisphere to the other
Commisurotomy
Refers to a surgical transection
of the corpus callosum, in order to study the hemispheres functioning directly
–> done to control severe epilepsy
In the 1950s Sperry and Myers did research on the corpus callosum.
What were their results ?
That the CC is critical for communicating between the left + right hemispheres
–> commisurotomy resulted in the right HP not learning what the left one had learned and vice versa
Epileptic seizures
Occur when the normal complex patterning of brain activity is disrupted + abnormal synchronous firing neurons occur over larger areas of the cortex
Why must split brain testing be interpreted with caution ?
Because
- The brains of these patients are not entirely normal, since they were affected with severe epilepsy
- Risky to draw big conclusions as the number of patients is small
- Subjects show a lot of variability among themselves
- Certain amount of cerebral reorganization may have occurred prior to surgery
- -> e.g. when one HP is damaged, the other may take over the functions - If each HP can learn independently, both will have different functions after the surgery that it did not have before
Unilateral testing
Involves testing the 2 hemispheres independently, where stimulus inputs are limited to one HP
What was the most commonly used method of unilateral testing in spilt brain patients?
Asking subjects to identify objects, that were out of sight in a box, by touch alone.
–> when right hand was used one could name it, when left hand was used they couldn’t
How did split brain researchers test the left + right hemispheres separately for recognition of visual stimuli ?
By using a “T-scope” test, where the subjects focused on a dot at the center of the screen, then a picture was flashed either to the right or left side of the screen
–> flash is so brief one couldn’t move the eyes, thus picture on the left side (LVF) could only be seen by right HP
THUS: if it was seen by left HP they could correctly name it; right HP = not
What is a “T-scope”?
A projection tachistoscope, which is used to lateralize the visual stimuli in a t-scope test
In the T-scope test, patients can usually not name or even see the visual stimuli presented to the left visual field ?
Why is that ?
Where is the difference in processing between the left vs right hemispheres ?
Right hemisphere processing
- recognizes
- understands concrete concepts
- initiates an automatic emotional reaction based on social learning
BUT: as verbalization occurs in left HP one cannot name the objects
e.g.: nude picture flashed to LVF elicited giggling, w/o the patient knowing why
Block design test
Requires the subject to use a set of colored cubes with a different color of paint on each side to construct a pattern that matches sample pattern in a picture
–> patients can do this quickly when using the left hand, but impossible what right one
Which hemisphere is superior to the other in visual recognition tasks ?
None really, as each has its individual superior qualities:
- Right hemisphere is superior in spatial tasks, where some sort of manipulation of objects in space is required
- -> manipulo-spatial superiority - Left hemisphere is superior in verbal + conceptual tasks
As each hemisphere seems to be able to think for itself, does each have separate centers of consciousness ?
Is each hemisphere independently conscious ?
Dual consciousness
Evidence for right HP consciousness includes:
- It can follow instructions + carry out tasks, by operating independently of the left HP
–> thus, intelligent behavior of the right HP is influenced by conscious but nonverbal thinking
- The alien hand
- -> voluntary action by the left hand, which shows a conflict between the 2 HPs - Cross cueing btw the HPs
- -> left HP is able to guess what the right has seen or felt by noticing its responses to the situation
Theory of liaison cortex
Ecccle
Suggests that language centers receive knowledge from an immaterial consciousness and can then make introspective verbal reports about it
–> but do not produce consciousness themselves
The fact that the 2 hemispheres can act independently in split brain patients, raises the question if consciousness is then also split among the 2, creating Dual consciousness.
Is there such thing ?
Yes (according to research by Sperry), as the right hemisphere shows perceptual awareness + conscious thinking by the criterion of a pattern of intelligent behavior
–> only introspective verbal report is missing
Name the evidence, Sperry presents in favor of right HP consciousness.
- Right HP could follow instructions then carry them out by operating independently of the left HP
–> intelligent behavior of the disconnected right HP is influenced by conscious + nonverbal thinking
- Alien hand
- -> voluntary action of the left hand, which suggests a conflict btw the 2 hemispheres - Cross cueing
- -> left HP os able to guess what the right one has seen or felt - Recognition in terms of emotional outbursts
Gazzaniga did not share the same opinion as Sperry.
Elaborate on this.
He argued that right HPs of split brain patterns are not conscious
–> right HPs consciousness is highly correlated with the presence of at least a moderately high degree of right hemisphere language ability
e.g.: patient P.S., the first with dual consciousness, but showed extensive linguistic skills
According to Gazzaniga, the mind/brain system is made up of modules.
What are modules ?
They refer to relatively independent functioning units, that are non-conscious as we do not have direct introspective access to them but can
- receive info
- compute/store/retrieve memories
- trigger emotional reactions
- produce behavior
Interpreter system
Gazzaniga
Occurs in close association with the linguistic system but is not identical to it and tries to interpret the diverse actions of the various modules to
a) explain why they occurred,
b) fit them into the narrative sequence of events of our lives
–> special module that only occurs in the left HP and is associated with consciousness
What is consciousness according to Gazzaniga?
The output of a special interpreter module which creates a sense of conscious unit
Gazzaniga changed his mind on when someone has dual consciousness.
Elaborate on how this shift occurred.
- One can only speak of dual consciousness if both HPs have linguistic properties
- As long as your left HP is able to interpret/verbalize the actions of the right HP (via interpreter system), one can speak of dual consciousness
What is Gazzanigas take on mental unity ?
Thinks it is an illusion
–> our actions are not all controlled by conscious executive system, so we do not do everything consciously
Unified consciousness
–> explains why they behave + fell normally
Unintegrated perception
Notion that the visual perception in split brain patients is largely unintegrated across visual fields
Integrated information theory
IIT
Suggests that consciousness arises when a system has a rich representation + its subsystems are strongly interconnected
Global workspace theory
Suggests that cerebral HPs house a global workspace (like headquarters) + only the info processed by the GW reaches consciousness
Recurrent processing
RP
Suggests that consciousness can arise through local RP btw cortical modules, even in the absence if global/integrative processes
–> only leads to phenomenal rather than access consciousness
Subcortical theory
Suggests that unified consciousness remains intact when a minimal number of axonal connections btw subcortical structures exists
Functional notion
Suggests that consciousness remains unified if a minimal amount of synchronization between the subsystems is preserved
–> regardless of whether the synchrony is driven by direct/indirect connections
