Touch/somatosensation
- According to GPT, sensory neurons from the right side of the body enter the left side of the spinal cord and then head toward the left hemisphere.
Auditory system
- According to GPT, sound signals from both ears are sent to both hemispheres, but typically with a preference for processing the left ear’s input in the right hemisphere and vice versa. Right auditory cortex is generally more involved in processing nonverbal sounds. Left hemisphere, on the other hand, tends to handle more language-related sounds and speech processing.
Other sensory like Pain and Temperature: still primarily cross over, according to GPT
Vision system
- Everything you see on the right side of your field of view → right visual field. The retina is divided into two halves: the nasal (inner) side and the temporal (outer) side. The information from the nasal retina of each eye crosses over to the opposite hemisphere at the optic chiasm.
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Macaque monkey: LGN → V1 → dorsally to PP, ventrally to IT
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LGN (lateral geniculate nucleus) of the thalamu
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V1 (the first cortical site of visual processing) and V2 respond to local image features
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V1: Every neuron have selectivity to a finite preferred location in the visual field. Nearby Hypercolumn have nearby preferred location. Within Hypercolumn, each neuron have selectivity to certain orientations (tilt), spatial frequency, colors, motion (direction and speed), face, ocular dominance (information from only one of the eyes, or both), disparity (as in depth analysis). Every neuron have a combination of prefered properties, with generalization gradient (a bit response with close but not exact prefered ones).
- Neurons fire in synchrony when bound (Gary & Singer, 1988): if one geon activates two neurons, they show strong synchrony.
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posterior Parietal cortex (PP)
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LOC (lateral occipital cortex). Respond iff stimulus has 3D interpretation (familiar or not) (fMRI). After V4.
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IT (inferotemporal cortex): mainly neurons that care about object shape independent of viewpoint, other respond to particular shapes in particular views.
- Respond to specific objects (single-unit recording).
- Neurons in posterior IT respond to geon properties and relations. (Tanaka, 2004)
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Homologous region (near hippocampus): respond to object (fMRI)
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Dorsal and Ventral pathway
- Patient DF (studied by Mel Goodale & Brenda Milner) lost LOC on both sides. Studied by Mel Goodale & Brenda Milner. Ventral stream damage (cut off by LOC). Report phenomenologically blind. No manage to Dorsal stream and therefore totally fine with interating with the worlds.
- A division of labor starts from retina but preserve in the whole visual system
- Magno system: large neurons, fast responses, high spatial frequency, insensitive to fine details, colorblind, motion-sensitive
- Parvo System: color-sensitive
- Equiluminant: giving equal number of photons per space and time
- Cat and dog have stronger magno system
Ventral and dorsal (how to interact; related to attention) pathways.
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Dopaminergic neurons related to priming. More and more in later vision regions.