Higher Order Brain Functions:Brain correlates, Handedness, Frontal lobe

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Neurological Basis of Behavior (PSY - 610)

Lesson45

Higher Order Brain Functions

Objectives:

The students would be familiarized with the Brain Hemispheric differences, Laterality, specialized role

of higher order brain functioning. Brain Damage and behaviors. Neuropsychological testing would also

be discussed

Brain correlates:

· Brain correlates of Learning and Memory, Amnesia, Verbal, Non verbal memory,

(Neuropsychological tools)

· Split Brain studies, Brain Hemispheric differences, laterality One brain/Two Brains? Brain

Damage and Plasticity

· Neuropsychological Tests

· Cerebral hemispheric specialization

Have you ever wondered why we have two lobes instead of one? Do they work as one brain or two? Are

they independent or do they communicate with each other. Is there any hemispheric specializations

(doesn't seem possible if you know that all neuroanatomical areas are bilaterally located, right?). But

did you know that brain areas are not exactly alike, and that each command center deals with the

opposite hemisphere. All fibers cross over except for the visual pathways, which are partially crossed.

This makes for a very complex research area, which was only focused in the last few decades.

Fact: The two lobes are connected by commissures.

Fact: There are specializations of functions.

Fact: There is cooperation as well as competition between the two hemispheres.

The earliest study reported on the "specialization" of brain hemispheric specialization was reported by a

French Neurologist Marc Dax. Dax presented his report on the findings of brain autopsies in a

conference in 1836. The interesting findings were that patients with strokes, who had speech problems

brain damage, all had damage to the left (none in the right hemisphere). Not until 25 years later did

some one bring this to the attention of the world obvious functional specialization is speech and

language abilities. In the mid-1800s, Paul Broca (a French neurosurgeon) reported two cases of aphasia

where the left hemisphere damage and speech production was identified. This is now known as Brocas

area (for speech articulation. Shortly afterwards, a German neurologist, Carl Wernicke, identified

another part of the left hemisphere primarily concerned with language comprehension (Wernicke's

area)

Two studies in 1959 and 1961 produced evidence that unilateral lesions produced deficits which were

evidence for brain hemispheric specialization.

Roger Penfield and his colleague Ebert (1959) reports on neurological patients and Russel and Sapir

(1961) on military personnel. Their results indicated that language was dominant in left hemisphere for

both the left and the right hemispheric dominant persons. (Remember: If you are right hemisphere

dominant, you are left handed, if you are left hemisphere dominant then you are right handed)

Brain Hemispheres: Two Brains or One?

The interest in further research in this area was stimulated accidentally. The major names in this area are

Penfield, Sperry, Gazzaniga, Milner, and many others who were pioneers in this area

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These studies used Commissurotomy, or Split Brain Procedure. This procedure uses a knife cut to sever

the commissures (including the Corpus Callosum) so that the two hemispheres cannot communicate

with each other. Interesting things happened. Outwardly these individuals seem normal, but sensitive

neuropsychological tests revealed that there were deficits. These tests were visual tactual verbal etc.

These tests were devised so that information could go to only one hemisphere. When words were

presented to the right visual field to reach the left hemisphere, the person could read it out loud (and also

write it). But then when it was shown to the right hemisphere the person reported he saw nothing. The

right hemisphere did not comprehend? Or perceive? It was thought that the left hemisphere did all the

work, and the right only was in a supportive role. It could not talk about what it saw, but when the

methodology was changed and the person was asked to pick out words from a group of alphabets or

objects form a group of objects, he picked the right ones!

When HEART was flashed on the screen in such a way that HE was in the right visual field so that it

input only the left hemisphere and ART input to the right. When asked what he saw, he stated HE, but

when asked to pick out words form a bloc of words given, he picked ART!

In other studies, when a split brain patient was walking through the room he acted as a blind man not

able to see while he walked, but he could identify objects in the areas when asked verbalize.

Thus do we have two brains or one, this is the question researchers asked, and what is the role of each

Brain Lateralization exists and the two halves of the human brain are not exactly alike. Each hemisphere

has functional specializations: some function whose neural mechanisms are localized primarily in one

half of the brain.

Handedness:

Handedness as

(a) The hand that performs faster or more precisely on manual tests, while others define it as

(b) The hand that one prefers to use, regardless of performance.

Majority of us are right handers (left hemisphere dominant), but there are reasonable number of people

who are left handed, and a small number is ambidextrous. Famous left handers are Leonardo Da Vinci,

Michelangelo, Napoleon, Alexander the great, and Baden Powel (ambidextrous: means can use both

with equal proficiency)

We also have dominance for foot (which foot used for kicking a ball or stepping on a stair first), eye (if

you are to use a telescope which eye would you use), ear (which ear do you use for listening to the

telephone). Dominance can be assessing by tests such as the Harris Tests of Lateral Dominance.

Asymmetry in faces is also reported, and Sackheim, Gur and Saucy (1978) took photographs of

expressed emotions and cut them and made composites, left-left (left half face) composite, right-right

composite (right half face composite), and had subject compared it with normal pictures for intensity of

emotions. They found that subjects reported the left-left faces more intense as compared to the right

right (why? Because the right hemisphere cannot speak, so images have to be more intense for the visual

input, whereas the left hemisphere can express itself through words.

How do we explain asymmetry?

There are two schools of thought a) one which believes that the: brain is equipotential for specialization

and at around 2 years of age the division of labor and specializations of the two hemispheres is

completed. The two hemispheres compete for control e.g. when both try to speak at the same time

stuttering occurs, Orton (1939).

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The other view point is that it is inborn and innate. This is even before any cultural or learning

influences can take place. For example, the planum temporale in the left hemisphere is larger in the

fetus. Therefore language is programmed to be in the left hemisphere

Tests for Language and Other Functions.

a) The WADA test: In this test Sodium Amytal, a barbiturate is injected through the carotid

arteries (main arteries which carry blood to the brain). This injection is made unilaterally (to one

hemisphere only) and the patient is required to speak a list of words. When the language

hemisphere is anaesthetized, the patient's speech becomes slurred, till it is blocked completely.

Milner branch and Rasmussen (1966) studied 212 patients like this to identify hemispheric

dominance for speech.

Zeidel lens (a specialized tachistoscope) was used to project images only to one hemisphere to

test verbal, visual, language and other asymmetries.

c) Dichotic listening tests: this is a test which sends out two different types of auditory signals to

the left and the right ear. For example, it can send alphabets to the left ear and simultaneously

send out numbers to the right ear. The subject is asked to repeat what they hear. The dominant

ear would hear, and therefore the list given by the subject would be of what the dominant ear

heard.

At present research is ongoing and it has been recognized that each hemisphere is specialized to work

alone and to work together.

Unilateral neglect, unilateral sensory neglect

This is very special disorder affecting response to one side of the body, somato-sensory, or visual field.

It is characterized by the patient not attending to one side only. This occurs as a consequence of damage

to either hemisphere in the spatial recognition the parieto-occipital area. This is a lateralized deficit i.e.

the patients don't respond to the side/ visual field opposite to damaged hemisphere. How can we assess

this simply by asking the patient to draw a clock face with numbers and showing a specific time let's

say 10 to 11 o'clock. And the patient draws only one half of the clock. In extreme cases the patients eat

from one side of plate, or shave one side of face, put lipstick on only half the face, interestingly if we

move them around they are able to describe the whole as their body moves.

More interesting and intriguing is the finding that we may have our frontal cortex controlling the rest of

the body and brain, as the Chief executive.

Frontal lobe

Orbit frontal: there is an interesting paper entitled No Longer Gage. This is about a person named

Phineas Gage who was a railway laborer. During construction, he had a major head injury where the rod

he was holding went right through his head. He survived but he changed personality, he was no longer

the same person. His family and friends said- he was no longer Gage. It was found that his injury to the

Orbito frontal areas changed him. There is now much research which indicates that judgment,

personality, fore sight, "conscience" reduced impulsivity are all located in this area. As a child grows,

inhibitions of the society and culture learning are all programmed in this area. Similarly control of all

emotions also resides here.

· Neuropsychological tests:

a) Luria, the father of Neuropsychology developed a series of tests to assess all abilities, but holistically

and by varying the tasks. For example to test handed ness, he would give the same task but use different

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modalities (visual, somato-sensory: touch, language command etc) different tests). These have been

incorporated in the Luria Nebraska Nueropsychological test Battery

b) Halstead Reitan Battery also tests such as the grooved pegboard, the tapping tests etc.

Harris tests of laterality

Research ongoing but both hemispheres work and compete, they are working together, sharing

information through corpus callosum this gives ones behavior a holistic, and a gestalt. Each

hemisphere needs the other, to provide back up information.

What if one hemisphere only? There have been cases where through surgery or brain injury or even

birth or developmental trauma, one hemisphere has been lost

If there is only one hemisphere, the remaining hemisphere can take over functions- without any

visible or other deficits. The earlier the traumas the more easily can the functioning take place. In

later life, it becomes difficult for the hemisphere to relearn.

Neuropsychological Tests

Neuropsychological assessment of cognition and other functions is carried out by trained

neuropsychologists (brain-behavior relationship specialists).

A formal interview is carried out initially followed by review of all medical and other history taking

records (whether they have been treated, birth traumas school records,) interviews of parents, or

relatives and neuropsychological testing using formalized procedure and tests

Neuropsychological testing aims to assess a patient's higher order functioning of attention, memory,

speed of information processing, language, visual-spatial ability, sensory processing, motor ability,

executive and intellectual functioning. This is based on the referral questions and also the previous

history of the patient. This also helps in developing a rehabilitation strategy.

The referrals for neuropsychological assessments are

a) Stroke patients

b) Head injury patients

c) Children with slow development or difficulties in speech, attention or learning

d) Chronic alcohol or substance abusers

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Some neuropsychological tests

There are several protocols available, the two well known batteries are a) The Halstead Reitan

Neuropsychological Battery is older and which takes about 8 hours for a patient to complete. The

second battery is the Luria- Nebraska Neuropsychological Test Battery which is developed by

American Neuropsychologists based on Luria's techniques. This is has a series of subtests but takes less

time and has more flexibility (qualitative information). These tests assess motor, sensory, visual

language, kinesthetic, attention, memory, receptive and expressive speech (speech sounds rhythm) tests.

Test also assess if the patient is following instructions through different modal tests

Two of the simplest tests which I have used which provide rich information are the Trails making A

and B: these are part of the Halstead Reitan Battery. They appear simple where the patient has to join

lines of various numbers in Part A and numbers and words in alternating sequence in Part B. Spatial

organization, grapho-motor speed, recognition of numbers, visual pursuit, vigilance and number

sequences is measured by this. Part A evaluates visual motor coordination and visual scanning as well

as short term memory. Part B measures higher order functioning as it requires alternating between

numbers and letters, ability to learn an organizing principle and apply it systematically, also verbal

problem solving, and planning action beforehand.

Thus, the Neuropsychological tests are effective tools for a trained person. These tests are used for

diagnosis, to identify deficits due to illness or injury, to assess learning problems, reasoning and

problem solving abilities, ability to understand and express language, memory and attention especially

post trauma, visual-spatial memory and organization, visual-motor coordination, and higher order

planning and organizing abilities.

Course Recap

We have completed the course today, and if we look where our lessons began.

a) We learnt about the development of behavioral Neurosciences as a discipline, the major

contributors to this discipline, and how it is made up of specializations from various field of the

hard sciences Chemistry, biochemistry, physics, biology and of course this is incorporated to

help us understand behavior- both at the lower level (of animals) and of humans

b) We learnt of the various stages of evolutionary development, of commonalities and differences

between man and other animals. We also learnt of how the brain developed form a single cell

layer to the complex form we have. The developmental journey with nature- nurture interaction,

where things can go as programmed if only the right environmental stimulation is given

c) You also learnt about the various neuroanatomical sites and their contribution to behavior,

NeuroChemicals and their effect (in some cases very serious psychopathologies and

physiological deficits can take place with a single molecule

d) We have learnt how motivational states are neuro-anatomically, neuro-chemically driven.

Hunger, thirst, sleep, without which we may not be able to survive let alone function

e) The journey into higher order functioning, language (its deficits) learning and memory

(amnesias), disorders such as apraxias, agnosias, aphasias, were also discussed giving you and

insight into the neuropsychological area

f) It ahs always been interesting to teach the brain-behavior relationships, I do hope this course

would help you understand your behavior as well as behavior of others better.

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There are excellent sites on the web for you to visit and learn more. Some of them are given in the

handouts, but others are as follows:

Central Nervous System Overview

Learn about an astonishingly complex system of creases, projections, fibers, branching cells, colors, and

connections known as the human nervous system.

http://www.brainconnection.com/topics/?main=anat/cns

Primate Handedness and Brain Lateralization

By M.K. Holder, Ph.D.

http://www.indiana.edu/~primate/

References:

1. Carlson N.R. (2005) Foundations of Physiological Psychology Allyn and Bacon, Boston

2. Pinel, John P.J. (2003) Biopsychology (5th edition) Allyn and Bacon Singapore

3. Bloom F, Nelson and Lazerson (2001), Behavioral Neuroscience: Brain, Mind and Behaviors (3rd

edition) Worth Publishers New York

4. Bridgeman, B (1988) The Biology of Behaviour and Mind. John Wiley and Sons New York

5. Brown,T.S. and Wallace.(1980) P.M Physiological Psychology. Academic Press New York.

6. Bradshaw J.L. and Mattingley, J.B. (1995) Clinical Neuropsychology: Behavioral and Brain

Sciences. ACADEMIC PRESS

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