Jan 18 Perception

• Mechanoreceptors send information to the spine, which then sends it to the somatosensory cortex.
• The cortical homunculus is a spatially organized map of the body for sensory and motor functions.
• Current evidence suggests an update of motor homunculus to include regions that control integrative, whole-body actions.
• Chemicals moving through the air pass through the olfactory epithelium to the olfactory bulb.
• Olfaction has a stronger link to memory and emotion than any of the other senses, which explains why the smell of cut grass can trigger a memory better than an image of grass.
• New research suggests that the sense of smell is also related to brain health and is an early symptom of dementia.
• Taste works with olfaction, explaining why things do not taste as good when our nose is stuffed.
• Taste buds are located on the tongue, palate, pharynx, and upper esophagus, and measure chemicals that have been ingested.
• Taste buds relay a message to the thalamus and then the primary gustatory cortex.
• Flavour (taste) is also affected by other senses, including vision, as evidenced by the fact that reddish colours are associated with sweet tastes and greenish colours are associated with bitter tastes.
• A Constructivist Theory of Perception is a top-down theory of perception that suggests perception is influenced by stored knowledge and context.
• Constructivist Theory is supported by knowledge and illusions, such as the Ponzo illusion, the monster illusion, and the world is lit from above.
• Bottom-up processing is when information from the eyes to the primary visual cortex propagates down the “what” and “where” pathways and does not require specific knowledge of the stimulus.
• Top-down processing is when information from final stages of visual pathway processing is sent back to the visual cortex to exert influence using knowledge or expectations for perception.
• Prosopagnosia is a type of Visual Agnosia where damage to the Fusiform Face Area (FFA) leads to a selective deficit in recognizing faces, keeping intact the ability to visually recognize other objects.
• In the case of Visual Agnosia, a probe is matched to long-term memory traces, looking for a match.
• In Template Matching Theory, every object has a ‘template’ in long-term memory, but this is considered too simplistic and computationally demanding.
• Agnosia subtypes include:

  • Apperceptive agnosia, which is a failure in recognizing objects due to problems with perceiving the elements of the objects as a whole
  • Associative agnosia, which is an inability to associate visual input with meaning.
• There is selective face processing in the brain.
• • Apperceptive Visual Agnosia is characterized by problems with perception and discrimination of objects
  • Associative Visual Agnosia is characterized by problems on tests that require accessing information from memory.
• In the case of a sheep farmer with prosopagnosia, he was unable to recognize or name famous faces, but could recognize and discriminate sheep with very high accuracy.
• Against Functional Specialization for Faces, it is argued that the FFA is special for faces or just discrimination.
• Damage to the Ventral Visual Pathway can lead to Visual Agnosia, which is characterized by difficulties recognizing everyday objects, often from damage to the Lateral Occipital Cortex.
• Theories of Visual Object Recognition suggest that perception involves processing basic visual features of an input, and that pattern recognition suggests we then add up these features and match it to existing patterns (concepts) stored in memory.
• Visual Agnosia can be selective to visual categories such as faces, indicating functional specialization within the ventral pathway.
• In Prototype Theory, a prototype is the average representation of an object concept, and recognition is determined by a ‘good enough’ match (resemblance), allowing for ‘flexible’ object identification.
• Bistable figures suggest that we can experience spontaneous subjective change in perception, directing us to understand what factors (constraints) are driving this effect or how we organize perception.
• There might be action specificity in the dorsal ‘where’ pathway, as selective damage leads to problems with certain types of actions.
• Damage to the Dorsal Where Pathway can also result in optic ataxia, where there are problems reaching for objects with the ability to name objects

  • ex. problems reaching for a cup of coffee but able to recognize coffee, problems pouring milk but able to recognize milk.
• The principle of Good Contour states that we perceive objects as continuous in cases where it is expected that they continue.
• Damage to the Primary Visual Cortex can result in blindsight, where there is no conscious awareness (explicit perception) of visual objects in the damaged visual field, but there is the ability to implicitly respond to questions about objects presented in the damaged visual field.
• Direct models propose a passive bottom-up approach to perception, stating that sensory information is rich enough for perception.
• Texture gradients in the AOA can provide information about your movement and distance.
• Damage to the Dorsal Where Pathway can result in akinetopsia, where there is visual motion blindness and the inability to see motion, instead, perceiving motion as a series of stationary objects.
• Direct Models require an ecological approach to understand perception, studying it in the real world (JJ Gibson).
• Topographical breakages in the AOA help see edges and define objects.
• Affordances in our environment provide cues indicating potential function of an object, these are perceived directly and immediately.
• The principle of Similarity states that we organize objects or features of a scene based on similarity.
• Scatter reflection in the AOA provides cues about the nature of the surface.
• The dorsal ‘where’ pathway in the brain processes spatial information, depth perception, estimating movement and direction of objects.