Memory and Cognition PSY 324 Chapter 2: Cognition and the Brain Part II: Localization of Function Dr. Ellen Campana Arizona State University

The Whole Brain Localization of function - Different parts of the brain serve different functions Localization of function - Different parts of the brain serve different functions Many, many ways to divide the brain Many, many ways to divide the brain Like an onion, many layers Like an onion, many layers Like a fractal, the closer you look the more complex it seems Like a fractal, the closer you look the more complex it seems Descriptions may seem contradictory and/or overlapping because of this Descriptions may seem contradictory and/or overlapping because of this

Cerebral Cortex Most important for Cognition Most important for Cognition

Cerebral Cortex Temporal Lobe Temporal Lobe Language Language Memory Memory Hearing Hearing Perceiving forms Perceiving forms Occipital Lobe Occipital Lobe Visual information (early processing) – feature detectors Visual information (early processing) – feature detectors

Cerebral Cortex Parietal Lobe Parietal Lobe Touch Touch Vision Vision Attention Attention Frontal Lobe Frontal Lobe Proportionately larger in humans than in other species Proportionately larger in humans than in other species Language Language Thought Thought Memory Memory Motor functioning Motor functioning

Subcortical Structures

Hippocampus Hippocampus Forming memories Forming memories Amygdala Amygdala Emotions, emotional memories Emotions, emotional memories Thalamus Thalamus Processing sensory information (vision, hearing, touch) Processing sensory information (vision, hearing, touch)

Hemispheres Brain separated into sides (hemispheres) Brain separated into sides (hemispheres) Corpus Collosum connects them Corpus Collosum connects them Structurally and functionally very similar Structurally and functionally very similar Lateralization – specific functions occurring in one hemisphere or the other Lateralization – specific functions occurring in one hemisphere or the other Note: Sperry studied “split-brain patients”, who had had their corpus collosum severed as a treatment for epilepsy. He shared Hubel & Weisel’s Nobel Prize for this work.

Lateralization Vision of left part of the world lateralized to the right side (opposite also true) Vision of left part of the world lateralized to the right side (opposite also true) Motor Control of left side of body lateralized to the right side (opposite also true) Motor Control of left side of body lateralized to the right side (opposite also true) Touch on left side of body lateralized to the right side (opposite also true) Touch on left side of body lateralized to the right side (opposite also true)

Lateralization Are there “right-brained” and “left-brained” people? Are there “right-brained” and “left-brained” people? Analytical/Logical processing (syntax of language) usually on the left side (not always) Analytical/Logical processing (syntax of language) usually on the left side (not always) Analogy and Broad Thinking usually on the right side (not always) Analogy and Broad Thinking usually on the right side (not always) Everyone has (and uses) both Everyone has (and uses) both Patients who have had a hemispherectomy Patients who have had a hemispherectomy Other side usually takes over missing functionality Other side usually takes over missing functionality Coglab “Brain Assymetry” Coglab “Brain Assymetry”

Localized Function Parietal Lobe Parietal Lobe Sensory Homunculus (near the front, somatosensory cortex) Sensory Homunculus (near the front, somatosensory cortex) Motor Homunculus (near the back, motor cortex) Motor Homunculus (near the back, motor cortex) These guys aren’t actually IN your brain, they’re representations of how much cortex area is devoted to different body parts

Sensory Homunculus Each side of the brain has a copy, which processes touch from the other side

Localized Function Parietal Lobe Parietal Lobe Sensory Homunculus (near the front, somatosensory cortex) Sensory Homunculus (near the front, somatosensory cortex) Motor Homunculus (near the back, motor cortex) Motor Homunculus (near the back, motor cortex) Temporal Lobe Temporal Lobe Wernicke’s Area – metaphor, meaning in language Wernicke’s Area – metaphor, meaning in language Broca’s Area – logical structure of language Broca’s Area – logical structure of language Fusiform Face Area (FFA) – specialized for faces (or is it things we’re experts at recognizing???) Fusiform Face Area (FFA) – specialized for faces (or is it things we’re experts at recognizing???)

Researching Localized Function Neuropsychology – comparing patients with localized brain damage Neuropsychology – comparing patients with localized brain damage Single dissociation– single patient has some things impaired, other things not impaired Single dissociation– single patient has some things impaired, other things not impaired

Single Dissociation: Phineas Gage Construction accident – 1848 Construction accident – 1848 Harlow (doctor) wrote a lot about his condition Harlow (doctor) wrote a lot about his condition Gage lived, could talk, act, and do all “normal” activities, but suffered impairment of emotional, social, and personal traits Gage lived, could talk, act, and do all “normal” activities, but suffered impairment of emotional, social, and personal traits Evidence for some separation of language and social traits, etc. Evidence for some separation of language and social traits, etc.

Researching Localized Function Neuropsychology – comparing patients with localized brain damage Neuropsychology – comparing patients with localized brain damage Single dissociation – single patient has some things impaired, other things not impaired Single dissociation – single patient has some things impaired, other things not impaired Broca’s Aphasics, Wernicke’s aphasics, Prosopagnosiacs Broca’s Aphasics, Wernicke’s aphasics, Prosopagnosiacs Double dissociation -- two (or more) patients show opposite single impairments Double dissociation -- two (or more) patients show opposite single impairments Broca’s & Wernicke’s Aphasics considered together Broca’s & Wernicke’s Aphasics considered together

Double Dissociation Form “The boy was pushed by the girl” Meaning “The apple was eaten by the girl” Broca’s Aphasics ImpairedOK Wernike’s Aphasics OKImpaired

What can we conclude? Double dissociation Double dissociation Two functions involve different mechanisms Two functions involve different mechanisms Two functions involve different brain areas Two functions involve different brain areas Mechanisms are independent Mechanisms are independent Single dissociation Single dissociation Two functions involve different mechanisms Two functions involve different mechanisms Two functions involve different brain areas Two functions involve different brain areas Mechanisms may not be independent Mechanisms may not be independent

Limitations of Neuropsychology At least for human processing, brain damage comes about from natural means (accident, etc.) At least for human processing, brain damage comes about from natural means (accident, etc.) Members of groups rarely have exactly the same damage (location or extent) Members of groups rarely have exactly the same damage (location or extent) No record of processing or brain organization before the damage No record of processing or brain organization before the damage Difficult to assess all possible types of functional impairment Difficult to assess all possible types of functional impairment Brain may actually reorganize following damage (called plasticity) Brain may actually reorganize following damage (called plasticity)

Imaging Methods EEG- Electrodes on outside of head continuously measure electrical activity EEG- Electrodes on outside of head continuously measure electrical activity PET- Radioactive dye injected, accumulates in different regions over time and can be read by a scanner. Essentially measures metabolism of neurons PET- Radioactive dye injected, accumulates in different regions over time and can be read by a scanner. Essentially measures metabolism of neurons fMRI- Brief magnetic pulses used to give a snapshot of ratio of oxygenated to deoxygenated blood (metabolism) fMRI- Brief magnetic pulses used to give a snapshot of ratio of oxygenated to deoxygenated blood (metabolism) TMS- New measure. Magnetic field can disable specific portions of the brain for a short time, simulating damage. TMS- New measure. Magnetic field can disable specific portions of the brain for a short time, simulating damage. Temporal resolution: Detail with respect to time Temporal resolution: Detail with respect to time Spatial Resolution: Detail with respect to physiology Spatial Resolution: Detail with respect to physiology

Image from an fMRI scan Image from a PET scan

Imaging Methods Spatial Resolution Temporal Resolution EEGPoorGood PETExcellentPoor fMRIGoodGood TMSGoodGood

Subtraction Technique Used for fMRI studies Used for fMRI studies Method similar to Donder’s study Method similar to Donder’s study Compared two situations that included different cognitive processes Compared two situations that included different cognitive processes Data = blood glucose level Data = blood glucose level Relative measure Relative measure Visual Stimulus (light flashing) Perception of the light Response Visual Stimulus (light flashing) Perception of the light Response DECISION

Subtraction Technique Activation in control condition is subtracted from experimental condition to get activity due to stimulation in the experimental condition Activation in control condition is subtracted from experimental condition to get activity due to stimulation in the experimental condition

The End Next up: Representation in the Brain Next up: Representation in the Brain