Week 1-Brain structure and function

Question 1

What are the 5 divisions of the human brain and structures within, evident from embryonic development through to adulthood?

Answer 1

1.Myelencephalon: Medulla- largely comprises tracts between the brain and spinal cord

2.Metencephalon: Pons (part of brainstem linking brain to spinal cord) and cerebellum

3.Mesencephalon: Tectum and tegmentum

4.Diencephalon: Thalamus and hypothalamus

5.Telencephalon: Cerebral cortex, limbic system and basal ganglia

Question 2

What’s the structure of the Cerebral Cortex?

Answer 2

-Composed of small unmyelinated neurons and grey matter (other layers are composed of large myelinated axons and white matter)

-Large convultions=fissures AND small convultions=sulci (both grooves which increase the SA)

-Ridges between fissures and sulci are called gyri

-Longitudinal fissures separate the hemispheres (remains connected by cerebral commissure inc. corpus callosum)

-Contains the NEOCORTEX and subcortical structures (e.g., hippocampus, limbic system and basal ganglia)

Question 3

What is the neocortex and how is it different to the cerebral cortex?

Answer 3

-Newest part of the cerebral cortex to evolve

-Cerebral cortex = largest part of telencephalon, composed of grey matter. Neocortex = largest part of cerebral cortex (90% of cerebral cortex is neocortex in humans). 10% is allocortex (contains hippocampus)

-Main difference is that NC has 6 layers and is the most developed in its number of layers and organisation of the cerebral tissues (specific to mammals)

-Humans have large neocortex ratio, which correlates with complexity of behaviour. For a large neocortex to evolve brain must evolve in size to support it

-Central and lateral fissure divide each hemisphere into 4 lobes (frontal, parietal, temporal and occipital)

-lobes are not functional units

Question 4

What are the 4 lobes of the cerebral cortex/neocortex + functions?

Answer 4

1.Frontal lobe: motor cortex (precentral gyrus) and complex cognitive functions (frontal cortex)

2.Temporal lobe: hearing and language, complex visual patterns and memory

3.Occipital lobe: visual processing

4.Parietal lobe: somatic sensations e.g., touch (post central gyrus), orientation and location of objects

Question 5

What is an enduring question in biopsychology?

Answer 5

What extent can the functions of the brain e.g., language, thought and movement can be localised to specific areas of the brain

Question 6

Who founded Phrenology?

Answer 6

Franz Joseph Gall (1758-1828) – famous proponent of localisation theory

Question 7

What is Phrenology?

Answer 7

-Comes from ancient greek “phren”=mind and “logos”=knowledge

-A “pseudomedicine” which attempted to divine intellectual intellect and personality by examining the skull assuming the surface reflects the development of various regions

-Formed over observation of classmates who could recite long passages with bulging eyes (verbal memory in frontal region in eyes)

-His lectures “cranioscopy” offended religious leaders and had to leave the country after being banned by Austrian government in 1802

Question 8

What did Gall discover

Answer 8

-27 total cranial regions corresponding to distinct mental traits

-Found regions responsible for murder and inclination to steal (felt criminals heads to “detect patterns”)

-Localised “destructiveness” just above the ear (as student with bump on ear liked torturing animals)

Question 9

What were Gall’s positive contributions?

Answer 9

-Believed the brain was the physical organ of the mind which governed mental faculties and feelings

-Proposed the idea that the cerebral cortex contains areas with localised functions proven later correct when Broca located a speech centre in 1861 and movement (motor cortex)

-Was the first to identify grey matter of the brain with active tissue (neurons) and white matter conducting tissue (ganglia)

-His views were modern at the time encouraging other scientists e.g. Pierre Flourens (1794-1867) the first scientist to use lesioning (the removal of tissue from the brain) as a means of experimentally studying the brains different regions

Question 10

Lesion Studies-What lead to Broca’s aphasia? Part 1

Answer 10

-1860s Paul Broca was interested in Gall’s claims that language functions were located in the frontal lobes of the brain

-51 year old patient had several neurological problems lacking speech for years except being able to say “tan”

-Tan’s autopsy revealed lesion on the surface of left frontal lobe

Question 11

Lesion Studies-What lead to Broca’s aphasia? Part 2

Answer 11

-2nd 85 year old patient had reduced speech to 5 days due to stroke 1 year prior

-Autopsy showed similar lesion area to “tan”

-This speech deficit is known as Broca’s aphasia

-Inferior frontal gyrus on left cerebral hemisphere (Broca’s area)

Question 12

Lesion Study- What lead to Wernicke’s aphasia?

Answer 12

-Broca said damage to Broca’s area should disrupt speech production NOT comprehension

-Carl Wernicke’s 10 clinical cases of language comprehension (1874) (next major discovery in localisation)

-He suggested that selective lesions of Wernicke’s areas produce a syndrome that’s primarily receptive e.g., poor comprehension of written and spoken language + meaningless speech still retaining superficial structure, rhythm and intonation of speech (essentially it’s a word salad)

-Localised by autopsy to the left temporal lobe

Question 13

How was further progress made in the localisation of language?

Answer 13

-Made by German Neurologist Kobinian Brodmann (1868-1918)

-Produced maps based on cytoarchitectural organisation of neurons in cerebral cortex using the Nissl method of cell staining

-52 areas of cerebral cortex identified that differ histologically in cells/structure aka Brodmanns functional areas of cerebral cortex

Question 14

What is the importance of Brodmann’s areas?

Answer 14

-They were based solely on their neuronal organisation, but have since been correlated closely to diverse cortical functions

-E.g., Broca’s speech and language areas were localised BA 44 and 45

-He provided a map based on collections of neuron types: which have been examined using lesion studies, experimental ablation and functional neuroimaging to map onto different brain functions

Question 15

What did Brodmann’s findings lead to?

Answer 15

-Moved from basic naming of lobes and structures by location to naming areas by function e.g., motor areas, visual cortex etc.,

-Multiple areas contribute to behaviour and these brain regions connect to each other to pass information

Question 16

What is the general classification of three functional areas?

Answer 16

Sensory, motor and association

Question 17

What are the functions of the prefrontal cortex? (very developed in humans)

Answer 17

-Belies (fails to) complex cognitive behaviour, conscious thought, social behaviour, decision making and personality

-Executive functions- higher-order cognitive functions- inhibitory control, updating memory, switching attention and word fluency

-Working memory and recall

-People with head injuries show deficits in these functions

Question 18

What do early studies in humans and monkeys report in regard to the prefrontal cortex?

Answer 18

-Large portions of it can be removed without loss of mental capacity + changes in behaviour (Hebb, 1936)

-Contributed to the widespread of psychosurgery e.g., lobotomy and leucotomy for psychiatric treatment in the first half of the 20th century

Question 19

Define lobotomy

Answer 19

The severing of connections from the prefrontal cortex to other areas of the brain

Question 20

Who was lobotomy introduced by?

Answer 20

-Antonio Egas Moniz who also won the Nobel Prize in physiology and medicine for the “discovery of the therapeutic value of leucotomy in certain psychosis”

-“Mixed” success as some patients became docile and could leave the hospital as it was more manageable BUT some committed suicide or was severely brain damaged

Question 21

What did David Ferrier (1986) find after performing experimental ablation of the frontal lobes on monkeys?

Answer 21

-Sensory faculties of sight, hearing, touch, taste and smell were all unimpaired BUT lost the faculty of attentive and intelligent observation

-Lesions (due to head injury or cancer) has lead to further localisations of function

Question 22

What are the 3 prefrontal subdivisions and their functions?

Answer 22

1.Dorsolateral prefrontal cortex (DLPFC): Working memory, rule-learning, planning, attention and motivation

2.Orbitofrontal cortex (OFC): inhibitory and emotional control and an inability to effectively function in the social domain

3.Ventrolateral prefrontal cortex (VLPFC): the human inferior frontal gyrus, different functions including spatial attention, inhibitory control and language

Szczepanski & Knight (2014)

Question 23

What is the primary motor cortex and how was it mapped in conscious human patients?

Answer 23

-Located in the precentral gyrus of the frontal lobe

-Mapped by Penfield and Boldrey (1937) doing neurosurgery with low-intensity electrical stimulations to points on the cortical surface noting which busy/bosy parts moved in response to stimulation

-Each stimulation activated a contralateral muscle and produced simple movement finding that the primary motor cortex is organised somatotopically

-Somatotopic layer referred to as the motor homunculus

Question 24

What is the effect of lesions on the primary motor cortex?

Answer 24

-Extensive damage in humans does not actually eliminate all voluntary movement

-Large lesions do disrupt the ability to move individual body parts independently of others AND reduce the speed, accuracy and force of movements

-Other movements able probably due to the association and secondary motor areas

Question 25

What are the 2 association motor areas?

Answer 25

1.Posterior parietal association cortex: integrates orientation information about body parts and external objects positions provides spatial information prior to movement

2.DLPFC: receives projections from posterior parietal cortex and projects to secondary motor cortex, primary motor cortex and frontal eye field

-DLPFC responds in anticipation of motor activity

Question 26

What are the sensory areas of the cortex?

Answer 26

-Consist of primary, secondary and association areas

-Primary areas receive input from thalamic relay nuclei

-Secondary sensory cortex receives input from primary sensory cortex of a system
OR other areas of secondary sensory cortex

-Association areas integrates info from more than one sensory system

-Posterior parts of brain behind central sulcus

-Large parts of the brain dedicated to processing sensory stimuli

-Postcentral gyrus: location of primary somatosensory cortex

Question 27

Define somatosensation

Answer 27

Sensations from the body

Question 28

How did Penfield et al. (1937) investigate somatosensation in the primary somatosensory cortex and what did they find?

Answer 28

-Electrical stimulation to cortical surface and fully conscious patients described what they’d felt

-Brodmann areas 1-3 (postcentral gyrus)- patients reported various sensations in their body

-Somatotopic organisation (sensory homunculus)

-Medial parts of the brain=legs Lateral parts of the brain=face sensations

-Distribution biased towards areas where sensory discrimination is high e.g., mouth, fingers

-SII - ventral to SI in postcentral gyrus - receives input from S1 (secondary somatosensory cortex)

Question 29

What are the effects of damage to the primary somatosensory cortex?

Answer 29

-Mild effects due to having multiple pathways

-Corkin et al. (1970) found a unilateral lesion of S1 in epileptics - 2 minor contralateral deficits (ability to detect light touch and reduced ability to identify objects by touch)

-Deficits were bilateral if lesion went into S2

Question 30

What is the association cortex?

Answer 30

Somatosensory signals conducted to the highest level of sensory hierarchy (prefrontal and posterior parietal cortex)

Question 31

Name 2 types of somatosensory agnosia and what they are

Answer 31

1.Astereognosia: Inability to recognise objects by touch (these are rare in the absence of simple sensory deficits)

2.Asomatognosia: The failure to recognise parts of ones own body- usually unilateral affecting left side of the body- associated with extensive damage to the right temporal and posterior parietal lobe (association cortex)

-The case of Aunt Betty

Question 32

What are the 3 main regions of the visual cortex and their functions and/or locations?

Answer 32

1.Primary visual cortex (located in the posterior region of the occipital lobes): receives most of input from visual relays of the thalamus

2.Areas of secondary visual cortex (prestriate and inferotemporal corices): receives input from primary visual cortex and visual association cortex

3.Association cortex (posterior parietal cortex)

Question 33

What happens if the primary visual cortex is damaged?

Answer 33

-A scotoma is produced (an area of blindness) in the corresponding area of the contralateral visual field

-Many patients with scotomas aren’t consciously aware of their deficits (sometimes visual completion can occur)

Question 34

Define contralateral

Answer 34

Relating to the side of the body that is opposite to that on which a structure of the brain occurs

Question 35

What are other areas of the visual system identified from fMRI?

Answer 35

-12 or so functional areas of human visual cortex have been identified

-30 in monkeys (24 secondary areas 7 association areas) and the neurons in each area respond to different aspects of vision e.g., colour, movement, shape etc.,

-Selective lesions produce different visual losses

-There are many connection pathways between these

Question 36

What are the Dorsal and Ventral streams?

Answer 36

-Information from the primary visual cortex project to areas of secondary visual cortex and association cortex via 2 major streams:

D: Projects up to the posterior parietal cortex (spatial stimuli e.g., location of objects and their movements/where?)

V: Projects across to inferotemporal cortex (characteristics of object e.g., colour, shape/what?)

Question 37

What happens if the posterior parietal cortex and inferotemporal cortex are damaged?

Answer 37

P: Can describe objects but can’t reach out and pick them up

I: Difficulty describing but no issue reaching out to pick them up

Question 38

What is Prosopagnosia (face blindness) (damage to secondary visual cortex)?

Answer 38

-Term coined in 1947 by German neurologist Joachim Bodamer from the Greek prosipon (side) agnosia (not knowledge)

-Difficulty recognising people that they have encountered many times

-Documented cases usually from brain damage to right fusiform gyrus during head trauma, stroke and degenerative disease

-Dr. P is described by Oliver Sacks in his book “the man who mistook his wife for a hat”

-An eminent musician with a progressive cognitive failure – he would get confused between objects. At the end of an interview with Dr Sacks – he confused the head of his wife with a hat, and grabbed her in an attempt to put it on his head

Question 39

Name 3 other sensory areas

Answer 39

1.Auditory areas – primary auditory cortex: superior temporal lobe, inside lateral sulcus (BA 41).

• Auditory association area: posterior to primary auditory cortex (BA22) – evaluates sounds (next to wernickes area)

2.Gustatory (taste) cortex (BA43) – roof of lateral sucus

3.Olfactory (smell) cortex – medial temporal lobe – connects to limbic system (emotions)

Association areas are where primary inputs are processed and comprehended

Question 40

What are Monoamine pathways in the brain?

Answer 40

-Neurotransmitter pathways have also been mapped in the brain

-Dahlstrom and Fuxe (1964) used immunofluorescence staining techniques to visualise the monoamine neurotransmitter pathways of serotonin, noradrenaline and dopamine

-Monoamine neurotransmitters emanate from brainstem and project to the forebrain and beyond

Question 41

Where are the left and right cerebral hemispheres not separate?

Answer 41

Where the cerebral commissures connect them to each other.

Question 42

Give example cases of lesions in the left hemisphere

Answer 42

1.Dax (1836) noted that 40 of his brain-damaged patients had speech problems (all had damage in LH)

2.Both of Broca’s aphasia patients had left hemisphere lesions in the frontal cortex then further 7 patients had lesions in Broca’s area localised to left PFC

3.Hugo-Karl Liepmann-apraxia associated with LH damage even though symptoms are bilateral

Research then focused on finding out lateralised functions to varying degrees of success

Question 43

Who has been studied for lateralisation of function?

Answer 43

-fMRI, PET, unilateral lesions, split-brain patients (language and motor abilities of LH are readily apparent)

-For many functions, there are no substantial differences between hemispheres AND when they do exist, it is only slight biases for one hemisphere

Question 44

True or false: Lateralisation is statistical rather than absolute

Answer 44

True, language is the most lateralised and certain functions display a superiority for one hemisphere above the other.

Question 45

Why are we still at a relatively early stage of relating anatomy to behaviour?

Answer 45

-Our understanding has developed from case studies, lesion studies and experimental ablation studies

-BUT structural and functional MRI can allow us to improve our understanding of structure - functional relationships in the brain in vivo

Question 46

What’s functional MRI?

Answer 46

-Shows activity as opposed to just the brain structure in MRIs

-Blood flow and neuronal activation are tightly coupled i.e., blood is pumped to an area of the brain when it becomes “active”

-It detects changes in blood flow (i.e., an increase) due to blood being diamagnetic (magnetised in a 180 direction) - therefore, we can image increases in brain activity

-It has helped us understand brain systems e.g., the reward system (different areas with different rewards e.g., food, sexual etc.,

Question 47

How is fMRI confirming and expanding our understanding of structure-function relationships? (Laird et al., 2009)

Answer 47

-Imaging word generation (dysfunctional in Broca’s aphasia)

-Meta-analysis of all word generation studies (66 papers, 197 experiments, 1552 coordinates) a widely used test of neuropsychological function

-Results revealed extensive convergence in large portions of the left inferior frontal gyrus centering on Brodmann’s area 44/45 (Broca’s area)

Question 48

How can fMRI help us understand brain plasticity following injury?

Answer 48

Hartwigsen and Saur:
-Functional imaging can identify brain plasticity changes following a stroke recovery

-These patients recovered language following a debilitating stroke and their fMRI data shows how their right hemispheres developed to compensate for left hemisphere damage

Question 49

What’s functional connectivity analysis?

Answer 49

-An fMRI analysis technique that allows to observe of which brain region correlates with one another in terms of their activation during a specific activity

-We can measure the BOLD signal from the entire brain during an interesting task encompassing the reward system e.g., a gambling task and compare with relevant groups e.g., substance abusers vs controls

-We can examine the BOLD signal changes associated with the trials when we expect system level activation (winning trials)

Question 50

What happened when the LSD experience was revealed by multimodal imaging? (Cahart-Harris et al.)

Answer 50

-20 participants given 75 micrograms of LSD or placebo, scanned at rest using fMRI

-LSD increases communication between normally segregated brain networks- magnitude of effect correlates with strength of subjective “ego dissolution” feelings of oneness - potentially beneficial in psychotherapy for patients to break free from rigid cognition - thought to underlie depression and addiction

-Limitations were that it was a small sample size and unpredictable

Question 51

What is Transcranial stimulation? : Frontier in neuroscience

Answer 51

A non-invasive method of brain stimulation relying on electromagnetic induction using an insulated coil placed over the scalp focused on an area of the brain thought to play a role in mood regulation

Question 52

What is Brain-Computer Interface?

Answer 52

Researchers are taking what we’ve learned about studies of the brain and localisation of function, to develop technologies to help people with body paralysis to communicate using electrical signals from their brains