Basic Brain Principles and Attention/Perception PSYC560 Cognition and Affective Processes

Getting Neurotic Neurons: cells specialized to receive and transmit information in the nervous system Cell body: contains mechanisms to keep cell alive Axon: tube filled with fluid which transmits electrical signal to other neurons Dendrites: (so named because of it’s resemblance to tree branches) multiple branches reaching from the cell body which receives information from other neurons Sensory receptors: specialized to respond to information received from the senses

This is Prettier

Basic, Basic Terms Transduction: receptors transform energy from environment into electrical energy Action potential Neuron receives signal from environment Information travels down the axon of that neuron to the dendrites of another neuron

Size Doesn’t Matter: Rate Does!

Neural Communication Synapse: space between axon and dendrite When the action potential reaches the end of the axon, synaptic vesicles open and release neurotransmitters which are picked up by the receiving dendrites Neurotransmitters: chemicals that affect the electrical signal of the receiving neuron Excitatory: increases chance neuron will fire Inhibitory: decreases chance neuron will fire

Who’s Your Grandma? Feature detectors: neurons that response best to a specific stimulus Hubel & Wiesel (1965) Simple cells: neurons that respond best to bars of light of a particular orientation Complex cells: neurons that respond best to an oriented bar of light with a specific length Neural code: information contained in the neural firing to any object/experience Specificity coding: representation of a specific stimulus by firing of specifically tuned neurons specialized to just respond to a specific stimulus Grandmother cell

Cat Sees Spot

Grandma Loves Controversy Too many different faces/objects to assign specific neurons to each one Even though neurons may respond only to specific types of stimuli, they still respond to a number of different types of that stimuli type Quiroga and coworkers (2005) Epilepsy patients viewed pictures of specific individuals/objects while hippocampal neuron firing was recorded Some neurons fired for just one person/object Distributed coding indicates a specific stimulus is distributed across a number of neurons

This is Your Brain: Some Gross Anatomy Cerebral cortex contains mechanisms responsible for most of our higher mental functions Temporal lobe: language, memory, hearing, perceiving forms Occipital lobe: vision Parietal lobe: touch, vision, attention Frontal lobe: language, thought, memory, motor functioning

More Gross Stuff The hippocampus and laying down new memories (the famous freak fencing faux pas) Amygdala: The emotional almond (engaged in emotionally laden memories)

Perception: Bottoms Up! Bottom-up processing Energy registers on receptors Incoming data Top-down processing Person’s knowledge, experience, expectations

What’s in an A? Template-matching Interactive activation model When pattern matches template, perceiver recognizing letter Problem: many different templates would be needed to recognize just one letter Interactive activation model Feature level Letter level Word level

A “K” By Any Other Shape… Doesn’t Match the Template!

The Latest Word Recognizing a single letter Recognizing a word Feature units activated Activation sent to each letter unit containing features activated Letter unit activated most indicates letter Recognizing a word Letter unit for each letter’s position in a word Letter units send activation to all words containing letters in correct positions Word superiority effect Letters easier to recognize when in a word Less easy to recognize letters in a non-word or presented alone

Palmer (1975) in the Kitchen First, shown target image (kitchen) Then “flashed” probes Mailbox ID’ed as loaf of bread Drum ID’ed as jar lid The moral of the story is context plays a major role in our largely reconstructive memories

Now Something Slightly Different Max Wertheimer bored at the train station in 1933 Let’s turn out the lights for this one…

Gestalt Laws of Organization Proximity Similarity Continuity Closure Orientation (“common fate” if in motion) Figure Ground Pragnanz (“Good Figure”)

Continuity Also typifies Pragnanz

Similarity Do we do this socially as well?

Proximity Ever assume people that are close together in space are somehow “together” in other ways?

Orientation

Figure Ground

Combining Figure Ground and Closure Do you see subjective contours?

How About Now?

Lateral Inhibition As the neurons in your retina fire “on,” it shuts off nearby retinal neurons. This allows us to detect edges This also presents a few perceptual anomalies, such as….

Phantom Shapes and Colors

Illusory Movement

Getting Seasick Yet?

3D Perception Monocular Cues Relative Size Occlusion Linear Perspective Shadowing Texture Gradient Motion Parallax

Occlusion and Relative Size

Linear Perspective

Shadowing Home experiment with Halloween masks

Texture Gradient

Motion Parallax Used frequently by cats preparing to pounce

Binocular Cues Accommodation (lens contraction) Convergence (ocular muscle contraction) Binocular disparity Stereoscopes (View Master) Parallax viewers 3D movies

The Amazing Color Change

Attention!

Did Someone Say My Name? The cocktail party phenomenon Early Selection Filter on the basis of physical characteristics Bottom up Late Selection Filter on the basis of meaning (all data is processed, then filtered) Top down

Sensorimotor Gating Filtration of non-relevant information in favor of important stimuli Often on the basis of environmental cues Prepulse Inhibition Disrupted by stimulants Commonly disrupted in individuals with schizophrenia (schizophrenia as an attention disorder?)

Perceptual Disorders: Blindsight Damage to striate cortex Often report seeing a small area of light and blind throughout most of the visual field Will react to and report details of objects in the visual field, though report no conscious sensation of seeing them Perception appears disrupted, but not processing

Perceptual Disorders: Agnosias Apperceptive Agnosia Form perception is damaged Cannot draw familiar objects Cannot describe objects Cannot match similar objects Associative agnosia Damage at a later “stage” Can draw, match, and descibe objects Cannot recognize them Cannot associate representative images with stored information Prosopagnosia Cannot recognize faces (even own reflection)

Questions? Thoughts?