the self and the brain Flashcards
theories of the mind
•Freud (19th century)
The mind is divided into irreconcilable parts. Much of its content and process is inaccessible to awareness.
•Experimental study of cognition (20th century)
Much of our learning and memory is implicit. We have poor awareness of mental processes. Our awareness of mental activity develops well after its actual onset.
Scientific work in the 20th century has destroyed ideas about the unity and accessibility of the mind. The view that has emerged is of the mind as a collection of interacting sub-systems, some relatively autonomous, some more associative, all working in parallel.
franz galls phrenology
Gall believed in functionally specialized brain areas corresponding to elements of personality or character. He also (erroneously) believed that their size, as indicated by the corresponding protrusion on the skull, indicated the relative prominence of that character or trait in the individual
occipital lobe
participates in vision processing. It processes and interprets everything we see.
parietal lobe
vision, touch, attention, action
frontal lobe
action, working memory, emotion, executive function
temporal lobe
hearing, language, memory, vision
cell membrane
the semi permeable membrane that encloses the neuron
dendrites
the short processes emanating from the cell body, which receive most of the synaptic contacts from other neurons
axon hillock
the cone shaped region at the junction between the axon and cell body
axon
the long, narrow process that projects from the cell body
cell body
the metabolic center of the neuron; also called the soma
The cell body pools the information arriving via dendrites and produces activation that travels down the axon to affect other cells.
myelin
the fatty insulin around many axons
nodes of ranvier
the gaps between sections of the myelin
buttons
the button like endings of the axon branches, which release chemicals into the synapses
synapses
the gaps between adjacent neurons across which chemical signals are transmitted
cingulate gyrus
which we will encounter when when studying emotion.
corpus callosum
a bundle of some 200 million axons that connects the left and right hemispheres of the brain.
The corpus callosum is essential to the coordinated operation of the mind as we know it because the two hemispheres have significant divisions of labour between them.
The corpus callosum carries two types of connections between neurons in the brain:
- Homotopic connections
- heterotopic connections
homotopic connections
are between spatially analogous locations across the hemispheres
heterotopic connections
connect cells from one area of one hemisphere to another area of the other hemisphere.
ipsilateral connections
between neurons that link areas within the same hemisphere.
What do these callosal connections do?
In some cases, they allow the functional areas in the two hemispheres to cooperate. This happens in vision, for example, where some cortical neurons have receptive fields that span both visual hemifields connections
callosotomy
Callosotomy has a good record of helping patients leave behind their debilitating condition and return to some semblance of normality. The aftermath of the procedure also presents an excellent opportunity to experimentally study what a mind divided along the hemispheres is like.
why is a wada test used
• The corpus callosum is essential to the coordinated operation of the mind as we know it
because the two hemispheres have significant divisions of labour between them.
• it is beneficial to know as much as possible about the patient’s hemispheric specialisation of critical psychological functioning to avoid chance of tissue damage during operation
what does a wada test involve
- one hemisphere of the brain is temporarily anesthetised by introducing sodium amytal into the left or right carotid artery.
- an angiogram is done to ensure that there are no blockages in blood flow. Then, sodium amytal is applied and the hemisphere is put to sleep.
- The doctor then tries to establish which aspects of speech, language and control are intact in the absence of the anesthetised hemisphere.
- They can also show a set of cards of pictures and words to recognise and remember. After the anesthetic wears off, the doctor can test for the patient’s level of recall and recognition memory. This gives surgeons a picture of the patient’s level of hemispheric specialisation of language and memory function.
Hemifield presentation
Exploits the structure of the optic radiation from the eye to the visual centres in the occipital lobe. Assuming that the person fixates their eyes straight ahead, things that are presented to the left half of the visual field are processed by the right hemisphere, and things presented to the right half of the visual field are processed by the left hemisphere. The duration of presentation has to be too short for the person to make eye movements and, as it were, take in both visual hemifields into both hemispheres.
Hemifield presentation study results
- LEFT hemisphere produces a verbal report, the RIGHT hemisphere doesn’t
- RIGHT hemisphere has perceived and processed the stimulus:
- It can direct the left hand to draw or pick up the stimulus object
^^What is presented to the left hemisphere (i.e., to the right visual hemifield) can be verbally reported. What is presented to the right hemisphere (i.e., to the left visual hemifield) cannot be verbally reported. However, the right hemisphere can show that it has seen and recognised the object if it is allowed to draw or pick up the object with the left hand (which is controlled from the right hemisphere).
block design test
The patient’s task is to simply copy the spatial pattern shown on the card with the blocks that are provided. When attempting to do this with the left hand (controlled by the right hemisphere), there is no problem. Solution is swift and accurate. When trying with the right hand (controlled by the left hemisphere), this task proves impossible. This shows the right hemisphere to be specialised for the spatial information-processing capabilities required for this task.
- The apparently integrated sense of self emerges from interacting brain systems
- Many brain processes are out of conscious awareness
- There are multiple ‘agencies’ competing for control of action and awareness
- Intuition is usually a poor guide to how the mind works
- The conscious experience of selfhood is the result of a story-telling exercise
- This is most likely hosted in the left hemisphere
