Mechanisms of perception, conscious awareness and Attention

• Hubel and Wiesel Nobel Prize winners, discovered the functional organisation and physiology of V1.
• Three types of neurons were distinguished: Simple cells, complex cells, and hypercomplex cells.
• V1 neurons transform information - they are orientation selective and direction selective.
• Also found that the V1 is organized in an orderly fashion

• Specificity and complexity increases with each level - e.g. receptor destruction, total loss of sense. Secondary sensory cortex destruction leads to a specific sensory deficit.
• Sensation - detecting a stimulus.
• Perception - higher order process intergrating, recognizing, interpreating stimulus.
• Damage: Primary visual cortex.

Evidence

• Damage to area of PVC - Scotoma.
• How to test: Fixed red dots flash on and off around different areas of visual field, maps the scotomas.
• Unaware - similar to completion fo blind spot to fill in the gaps.

Blindsight

• The ability to respond to a visual stimulus even with no conscious awareness (due to a scotoma). 
• May be that some connections still exist in V1, allowing for reactions without awareness. 
• May be that this message gets to the brain that do not pass through the scotoma.

• Each of the three levels of cortex contains functionally distinct areas - i.e. respond to different aspects of the stimuli.
• Magnocelluar pathway, colour in-sensitive in LGN, orientation selectivity in V1, processing visual motion MT.
• Parvocelluar, parvocelluar LGN layers show colour opponency, V1 complex cells processing visual object shape.

• Secondary - input mainly from primary.
• Association - input from more than one sensory system, usually from secondary sensory cortex.
• Macaque monkeys - 30 different PV areas, 24 secondary areas, 7 association areas all processing visual information.
• Evidence - Akinetopsia

Object discrimination task/Landmark discrimination task

• Bilateral lesion to the temporal lobe lead to a deficit in object discrimination.
• Bilateral lesion to parietal lobe leads to deficit in location discrimination.

Double disassociation

• Damage to the ventral stream - no conscious perception, but can interact with objects (the woman that could grasp objects she did not consciously see).
• Damage to the dorsal stream - can consciously see objects but cannot interact with that - the case of AT, the woman who could not accurately grasp unfamiliar objects that she saw.

• Association - input from more than one sensory system, usually from secondary sensory cortex - most of the cortex surface.
• Responsible for the complex sensory processing.
• Interactions between input (primary sensory systems) and output (generation of behaviour).
• Known as cognition - means the process by which we come to know the world.