Lecture 20: Attention

Cocktail party effect

A listener can attend to one voice in a noisy conversation and ‘tune out’ other simultaneous sound signals

At least some information in the unattended channel is still processed → Attending to your name when it is mentioned

Collin Cherry 1950s

• Presented different dialogues to each ear at the same time

• Attend to only 1 of the inputs & immediately repeat that content

• Tested subject’s ability to report the content of the other, unattended stream

Endogenous attention

voluntary attention tasks

• Subjects consciously direct attention to a particular aspect of the environment

→ Following an experimenter’s instruction + Fulfilling a self-generated desire

Exogenous attention

involuntary attention tasks

Stimuli arising from events or conditions in the environment that attract attention automatically

→ Unexpected noise, flash of light, movement, or other salient stimulus causes a shift of focus

Contralateral neglect syndrome

Typically due to right-side lesion of the parietal association cortex

Right hemisphere dominates attention for both sides (→ lesions on left side can be compensated)

• Left hemisphere is occupied with language.

Attention neurons

Located in the parietal cortex

• Objects can be made salient; e.g. objects change their color or luminance (bottom-up processing), or instructions make objects more important (top-down processing)

• Parietal neurons respond more intensely to attended objects than to unattended ones

Frontal cortex

Responsible for eye movements, attention direction, task switching

Brainstem

Superior colliculus → pulvinar (thalamus) → parietal cortex

frontal eye field (FEF)

Normal function is to generate eye movements to locations in visual space that warrant attention

Stimulation of this while the monkey attended the fixation point caused eye movement to the expected location and increased neural activity at the recording site

Frontal-parietal attention network

• Activated both endogenously and exogenously

• Thought to modulate activity in the sensory cortices and other brain regions

• Results in more effective processing of some inputs and a less complete processing of others

Balint’s Syndrome

Three characteristics:

• Simultanagnosia → the inability to attend to and/or perceive more than one visual object at a time

• Optic ataxia → the impaired ability to reach for or point to an object in space under visual guidance

• Oculomotor apraxia → difficulty voluntarily directing the eye gaze toward objects in the visual field with a saccade

Simultanagnosia

the inability to attend to and/or perceive more than one visual object at a time

Optic ataxia

the impaired ability to reach for or point to an object in space under visual guidance

Oculomotor apraxia

difficulty voluntarily directing the eye gaze toward objects in the visual field with a saccade