Cog Lec 11

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