Are are the 5 types of threshold
Perception threshold- weakest stimuli can be detected
Absolute threshold- lowest level detected
Recognition threshold- detected and also recognised
Differential threshold- change in detected stimuli that can be perceived
Terminal threshold- level beyond which stimuli no longer detected
Describe stereognosis
- ability to understand object by touch
- segregated LTM info arrives in contra cortex (somatotopy maintained)
- info combined to form precept
Describe Asterognosis
- impaired object recognition
- intact perception
What did micromapping reveal
- Columnar and topographical organisation of cortex
- Neuronal populations have defined
- modalities
- adaption rates
- receptive fields (larger than primary afferent due to convergence)
- grouped by function
Describe the columnar arrangement of the somatosensory cortex
- columns relate to specific location and receptor type
- excitatory and inhibitory connections lead to ‘feature extraction’
Role of Pyrmidal cells/ stellate cells
Pyramidal: longer axons to connect parts of the brain
Stellate cells: shorter axons to transfer info in the cortex
What layer does somatosensory Info enter
From thalamus to layer 4
Where is the primary somatosensory cortex located
- Post-central gurus
2. In Parietal lobe
Describe labelled line theory
- Overlapping receptive fields from Rapid adapting and SA receptors project to separate alternating columns
- Receptive field gets larger at each level of processing
What are the 3 types of feature detection neurones
- motion sensitive
- direction sensitive
- orientation neurones
How is direction sensitivity produced
- Excitatory receptive fields are aligned along preferred axis
- If stimuli is not preferred, it will hit an inhibitory field first and no firing will occur
