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Neuroimaging of occipito-temporal cortex
Activation during
object recognition
face perception
place perception
human body perception
•Object selectivity
•High tolerance: Size, illumination, rotation, etc
Secondary somatosensory cortex
•forms part of the parietal Operculum
•Also somatotopically organised
•Receives input mainly from SI but also directly from thalamus
•Has bilateral representation of the body
Requirements for multisensory integration
Spatial congruency
Temporal congruency
Inverse effectiveness
Superior Colliculus
has the spatial maps
do not output a specific location in space, but give a “movement vector”.
crucial for crossmodal integration from the various modalities.
Most single-cell studies focus on the SC
Temporal Congruency
•Visual stimulation travels faster than sound.
•However, visual processing (~ 30ms) takes longer that auditory (~2 ms).
•To make up for discrepancies there is a temporal binding window
Temporal binding window
Stimuli are integrated within a window of time to compensate for the physical timing discrepancy between sensory inputs
Two beliefs of the development of crossmodal maps
Sensory modalities are well-differentiated from one another at birth, and that associations among them must be learned
At birth, all sensory input is intertwined. Through development, these areas are separated, developing separate sensory areas
Synesthesia
an experience in which stimulation in one sensory or cognitive stream leads to associated experiences in a second, unstimulated stream
Brain activation from infant to adult
areas of activation decrease due to developing brain efficiency
Modality appropriateness hypothesis
We utilize the modality that is appropriate for the task.
Spatial task = visual modality
Temporal task = auditory modality
Touch task = tactile modality
Maximum likelihood ratio
We will integration information from the senses in a statistically optimal fashion (ie. most reliable).
Visual modality: Spatial processing
Auditory modality: Temporal processing
Tactile modality: weak spatial/temporal processing