Lecture 7 Flashcards
Figure 5.7: Brain of a human cadaver.
(a) Dorsal view looking down on the top of the brain. Note that the deep longitudinal fissure divides the cerebrum into the right and left cerebral hemispheres. (b) Sagittal view of the right half of the brain. All major brain regions are visible from this midline interior view. The corpus callosum serves as a neural bridge between the two cerebral hemispheres.
Cerebral cortex organization
Highly developed, 80% of total brain weight
2 hemispheres connected by corpus callosum, 300 mio axons
Outer shell grey matter, central core white matter
Tracts and nuclei –> integration between different regions, and initiation of neural output at synapses
4 lobes, 4 functional areas
- No part functions in isolation
Occipital lobes
Temporal lobes
Parietal lobes
Frontal lobes
Occipital lobes:
posteriorly, initial processing of visual input
Temporal lobes:
laterally, auditory perception
Parietal and frontal lobes separated by
the central sulcus
Parietal lobes:
receiving and processing sensory input
Frontal lobes:
- voluntary motor activity
- speaking ability
- elaboration of thought
Figure 5.8: Cortical lobes.
Each half of the cerebral cortex is divided into the occipital, temporal, parietal, and frontal lobes, as depicted in this lateral view of the brain.
Figure 5.9: Functional areas of the cerebral cortex.
(a) Various regions of the cerebral cortex are primarily responsible for various aspects of neural processing, as indicated in this lateral view of the brain. (b) Different areas of the brain “light up” on positron-emission tomography (PET) scans as a person performs different tasks. PET scans detect the magnitude of blood flow in various regions of the brain. Because more blood flows into a particular region of the brain when it is more active, neuroscientists can use PET scans to “take pictures” of the brain at work on various tasks.
Figure 5.10: Somatotopic maps of the somatosensory cortex and primary motor cortex.
(a) Top view of cerebral hemispheres showing somatosensory cortex and primary motor cortex. (b) Sensory homunculus showing the distribution of sensory input to the somatosensory cortex from different parts of the body. The distorted graphic representation of the body parts indicates the relative proportion of the somatosensory cortex devoted to reception of sensory input from each area. (c) Motor homunculus showing the distribution of motor output from the primary motor cortex to different parts of the body. The distorted graphic representation of the body parts indicates the relative proportion of the primary motor cortex devoted to controlling skeletal muscles in each area.
Parietal lobes:
What type of processing occurs here?
- somatosensory processing
Somatosensory cortex: somesthetic (touch, pressure, heat, cold, pain etc) and proprioceptive (position of body) input
Projected into specific region: sensory homunculus: relative proportion of cortex dedicated to specific area
Figure 5.10: Somatotopic maps of the somatosensory cortex and primary motor cortex.
(a) Top view of cerebral hemispheres showing somatosensory cortex and primary motor cortex. (b) Sensory homunculus showing the distribution of sensory input to the somatosensory cortex from different parts of the body. The distorted graphic representation of the body parts indicates the relative proportion of the somatosensory cortex devoted to reception of sensory input from each area. (c) Motor homunculus showing the distribution of motor output from the primary motor cortex to different parts of the body. The distorted graphic representation of the body parts indicates the relative proportion of the primary motor cortex devoted to controlling skeletal muscles in each area.
Somatosensory cortex
Receives input from opposite side
Damage to eg right cortex: left sensory deficit
Thalamus: awareness for sensation without localization and intensity
Somatosensory cortex: source and level of intensity, spatial discrimination –> shape etc
Sensory input projected to higher sensory areas for further analysis (concomitantly texture, shape, position etc)
Sensation processed into perception
Primary motorcortex
Voluntary control over skeletal muscle movement (crossing at pyramids)
Motor homunculus: representation ~ precision and complexity of motor skills
Motorunit: 1 motorneuron with its muscle fibers (10-1000 muscle fibers, eye vs back)
However: does not initiate itself voluntary movement (supplementary motor area: complex patterns like opening/closing hand, premotor cortex: orienting body toward specific target, and posterior parietal cortex: movement in spatial context)
Cerebral Cortex has three areas:
Supplementary motor area
Premotor cortex
Posterior parietal cortex
Supplementary motor area
Plays preparatory role in programming complex sequences of movement
Complex patterns of movement:
- Opening or closing hand
Premotor cortex
Important in orienting the body and arms toward a specific target
Posterior parietal cortex
- Lies posterior to primary somatosensory cortex
- When either of these areas is damaged, one can’t process complex sensory information to accomplish purposeful movement in spatial context
ie: manipulating eating utensils
Figure 5.9: Functional areas of the cerebral cortex.
(a) Various regions of the cerebral cortex are primarily responsible for various aspects of neural processing, as indicated in this lateral view of the brain. (b) Different areas of the brain “light up” on positron-emission tomography (PET) scans as a person performs different tasks. PET scans detect the magnitude of blood flow in various regions of the brain. Because more blood flows into a particular region of the brain when it is more active, neuroscientists can use PET scans to “take pictures” of the brain at work on various tasks.
Somatotopic maps
Not static but dynamic
Precise distribution unique and individual
Genetic, developmental and use-specific
String instrument musician, sms/touch screens
Language
In vast majority of people: areas for language in left hemisphere (can be transferred in age <2 if damage occurs)
Written/spoken/heard words
–> symbolism –> ideas/concepts
Involves: speaking ability (expression) and comprehension (understanding meaning)
Broca’s area vs Wernicke’s area
Broca’s area VS Wernicke’s area
motorcontrol vs comprehension, choice, sequence
Wernicke’s area receives input from:
primary visual cortex, primary auditory cortex
Figure 5.11: Cortical pathway for speaking a word seen or heard.
The arrows and numbered steps describe the pathway used to speak about something seen or heard. Similarly, appropriate muscles of the hand can be commanded to write the desired words.
Language disorders
Damage Broca’s area: understand spoken and written word, but cannot articulate words
Damage Wernicke’s area: cannot understand spoken or written word, but can speak fluently (without sense)
Damage=aphasias (mainly through stroke)
Speech impediments: weakness/incoordination of vocal apparatus
Dyslexia: inappropriate interpretation of words
Association cortex (“silent” areas)
Higher functions: processing in 3 association areas
Prefrontal association cortex
Parietal-temporal-occipital association cortex
Limbic association cortex
Prefrontal association cortex:
planning, decision-making, thinking, creativity, personality traits
Parietal-temporal-occipital association cortex:
pools somatic, auditory and visual sensations (to get the complete picture)
Limbic association cortex:
motivation, emotion, memory
Figure 5.12: Linking of various regions of the cortex.
For simplicity, a number of interconnections have been omitted.
Cerebral Hemispheres
2 hemispheres complement each other
Left cerebral hemisphere dominance - Associated with “thinkers”
Right hemispheric skills dominate in “creators”
Left cerebral hemisphere
- Excels in logical, analytic, sequential, and verbal tasks
> Math, language forms, philosophy - Tends to process information in fine-detail way
Right cerebral hemisphere
- Excels in nonlanguage skills
> Spatial perception and artistic and musical talents - Views the world in a big-picture, holistic way
