Somatosensory Cortex Flashcards
What are the two main somatosensory areas in the cortex?
Primary somatosensory cortex
Secondary somatosensory cortex
What does the somatosensory cortex do?
Integrates information from all over the body
What is the primary somatosensory cortex?
Receives projections from the thalamus
Begins the process of constructing perceptions from somatosensory information - starts the initial process of constructing perceptions
What is the secondary somatosensory cortex?
Located behind the primary somatosensory cortex - continuous the construction of perceptions, projections do the frontal cortex - integrates of information
What did Penfield find?
Stimulated the cortical surface with large electrodes and recorded response, wanted to locate source of seizures. Studies suggested that there was a single somatosensory homunculus (representation of the human body) in the cortex. Useful for understanding functional layout of the cortex
Did it while patient was awake
What receptors aren’t in the brain?
Nociceptors - which is why the cortex can be touched and people don’t feel pain
What did Kaas find?
Penfields technique stimulated loads off neurons at once, so couldn’t just locate a few
In this study, monkeys had electrodes inserted which measured responses from single neurons - better spatial resolution than Penfield. Four separate somatosensory homunculi was found
What are the 4 areas Kaas found?
Area 3a - muscles
Area 3b - skin - slow
Area 1 - skin - fast
Area 2 - joints, pressure
Why is information segregated?
It all needs to be segregated as we need to distinguish from different kinds of sensory stimuli coming from different sources
What does hierarchal organisation mean?
Perceptions constructed from sensations depend on a hierachical organisation in the somatosensory cortex. Area 3a and 3b project to 1, which projects to 2. With each successive relay of information, the size of the receptive field and synthesis increases. Somatosensory info is segregated and synthesised with each relay
Neurons have to ingegrate all of the info from different areas
What does damage to the primary somatosensory cortex result in?
Impairments in:
Pressure sensitivity, proprioception, hapsis (ability to identify objects by touch), and simple movements (e.g., reaching and grasping)
What happens after damage?
Reorganisation because of platicity
Following damage to the arm, the cortex that was devoted to the arm becomes sensitive to the face - instead of getting info from arm, getting info from face instead - brain is reorganising neural pathways after damage, experiences, memory etc
