1. Somatosensory Cortex
   1. Use- dependent & Impermanent
   2. Postcentral Gyrus aka primary somatosensory area (SS1)
      1. detect: incoming sensory info from periphery, not responsible for data interpretation
      2. all sensory data travel thru thalamus before postcentral gyrus
      3. site of sensory homunculus
      4. Lesions: loss of sensation of contralateral body part, depends on which sensory was damaged
      5. Sensory Homunculus
         1. cortical representation of every body part's sensation and is located at postcentral gyrus
         2. somatotopic organization of body sensation from contralateral side of body
         3. Plasticity if injury or disease
   3. Seconday Somatosensory Area (SS2)
      1. interpretation of sensory info, meaning is attached to incoming sensory data, Located: posterior to postcentral gyrus
      2. Lesions: tactile agnosia- inability to attach meaning to sensory data
         1. Ex. astereognosis, 2-point discrimination disorder, agraphesthesia & extinction of simultaneous stimulation
   4. Two Classification of Sensation
      1. Primary
         1. pain, temp, light touch, pressure, vibration & proprioception
      2. Cortical
         1. mediated by SS2 & posterior multimodal association cortex
         2. Tactile Agnosias
            1. Astereognosis: inability to identify objects by touch, cortical interpretation impaired
            2. 2-point discrimination: can't determine whether you've been touched by 1 or 2 points, sensory anatomy intact, cortical interpretation impaired. Eval: aesthesiometer
            3. Agraphesthesia: cannot interpret letters written on contralateral hand of affected side, intact sensory anatomy, cortical interpretation impaired
            4. Extinction of simultaneous stimulation: aka double simultaneous extinction, cannot feel tactile sensation on involved side, neurons that carry tactile sensation from involved side are cortically overridden by neurons from uninvolved side.
            5. Abarognosis: cannot accurately estimate weight of objects in relation to each other, intact sensory anatomy, cortical interpretation impaired
            6. Atopognosia: cannot localize exact origin of sensation, sensory anatomy intact, cortical interpretation impaired
2. Visual Cortex
   1. Primary (V1)
      1. receives info from optic tracts: lateral geniculate nuclei of thalamus & superior colliculi of midbrain. Detect: visual input shape, color, orientation, & directon (not interpretation) Location: posterior region of occipital lobe
      2. Lesions
         1. loss of sight despite intact visual anatomy
      3. Lesions produce cortical blindness
         1. visual info may be rerouted to visual associated areas rather than first proceeding to V1
   2. Visual Association Areas (V2 & Higher)
      1. more than 30 specialized areas, interpretation of visual input meaning is attached, Dependent on acquisition of experience
         1. Only develop with direct experience & use. Ex. depth perception.
         2. Sequence of color vision: V1 (detects) to V2 (further process to identify) to V4 (interprets color info)
      2. Lesions: visual agnosias inability to attach meaning to visual data
      3. V2
         1. sends info from V1 to appropriate association for interpretation, process info for refinement. Specialized in analyzing spatial characters, color, figure-ground properties and orientation
      4. V3
         1. interpreting form discrimination, ability to recognize shapes
         2. Lesions: no complete loss of vision, forms a ring around V1 & V2, if large enough it can destroy V1 and cause blindness
      5. V4
         1. interpretation of color, line orientation, and geometric pattern
         2. Lesion: produces achromatopsia-people only see shades of gray (not color blindness), people cannot recall or bring up in memory what colors look like. If retinas and V1 intact form, depth and motion are preserved
      6. V5
         1. interpret visual motion (objects in motion)
         2. Lesion: Akinetopsia people neither see nor understand the world in motion ( it appears to vanish), Color & form intact
   3. Two Visual Cortical Streams
      1. Dorsal
         1. info runsa dorsally from V1 to parietal lobe and is responsible for analysis of visual motions & actions
      2. Ventral
         1. info stretches ventrally from V1 to temporal lobe & responsible for perception of visual world and object recognition
   4. Visual Regions Connect Together & Project to Surrounding Structures
      1. all connect directly & reciprocally. Visual memories are made
3. Somatosensory & Visual Cortices
4. Tactile Agnosia
5. Auditory Cortex
   1. Primary (A1)
      1. Detect: sounds from environment, sends info to auditory association areas for interpretation Located: insula in temporal lobe
      2. Lesion: unilateral deafness only in one hemisphere, bilateral both hemisphere, may still have ability to process data on unconscious level Ex. ability to startle to a loud noise but not consciously hear
      3. auditory pathway of inferior colliculi of midbrain and medial geniculate nucleus of thalamus
   2. Auditory Association Areas
      1. Responsible for interpretation of auditory data (ex. animal sounds, language) located throughout cortex
      2. Lesion: auditory agnosia- inability to attach meaning to specific sounds
   3. Broca Area
      1. Neural region mediates motoric aspects of speech and responsible for verbal expression of language. Located in left hemisphere just above lateral fissure, within inferior frontal gyrus of premotor area
      2. Lesion: expressive aphasia or nonfluent speech- understand what is spoken to them but cannot form meaningful sentences.
   4. Wernicke Area
      1. Language area responsible for comprehension of spoken word. Located: only in left hemisphere and sits within superior temporal gyrus in temporal lobe
      2. Lesion: receptive aphasia- cannot understand what is spoken to them, they can produce intact sentences (although the meaning of words does not relate to anything that others have said to them)
6. Auditory Cortex