Cog Neuro midterm

Methods of Research

Positron Emission Tomography (PET)  

• Procedure: radioactive tracer (often glucose with Fluorine-18) is injected into the body. The tracer accumulates in areas of high metabolic activity (e.g., tumors, brain regions). Detects gamma rays from the annihilation of positrons and electrons, creating 3D images of these areas.  

• Science: The radioactive tracer decays, emitting positrons. When positrons meet electrons, they annihilate, releasing gamma rays that the scanner detects, allowing visualization of metabolic processes.

Functional Near-Infrared Spectroscopy (fNIRS)  

• Procedure: Near-infrared light is emitted from sources placed on the scalp and penetrates the skull to reach the brain. Detectors measure the light absorbed by oxygenated and deoxygenated hemoglobin, providing insights into brain activity.  

• Science: Hemoglobin absorbs near-infrared light at different rates depending on oxygen levels. Increased brain activity raises oxygen consumption, causing changes in blood oxygenation, which fNIRS detects.

Transcranial Magnetic Stimulation (TMS)  

• Procedure: A magnetic coil is placed on the scalp, delivering short magnetic pulses to stimulate specific brain areas.  

• Science: Magnetic pulses induce electric currents in the brain, modulating neural activity. This can either increase or decrease brain excitability, helping treat conditions like depression.

Transcranial Electrical Stimulation (TES)  

• Procedure: Electrodes are placed on the scalp, delivering weak electrical currents (tDCS, tACS, tRNS) to modulate brain activity for cognitive enhancement or motor recovery.  

• Science: TES alters brain activity by modulating the membrane potential of neurons, affecting their firing rates and influencing cognitive or motor functions.

Electroencephalogram (EEG)  

• Procedure: Electrodes placed on the scalp detect electrical signals produced by large groups of neurons. The signals are amplified and recorded.  

• Science: Neurons generate electrical fields during activity, which are strong enough to be detected on the scalp. EEG measures voltage fluctuations caused by ionic currents in neurons.

Event-Related Potential (ERP)  

• Procedure: A series of stimuli (e.g., images, sounds) are presented, and EEG signals are recorded in response. The data is averaged to isolate neural responses linked to each stimulus.  

• Science: The brain processes stimuli in time-locked responses, generating distinct neural components. These components can be analyzed to study sensory, cognitive, and motor processes.

Diffusion Tensor Imaging (DTI) & Tractography  

• Procedure: DTI uses MRI to measure the movement of water molecules in the brain, especially along white matter fibers. Tractography reconstructs and visualizes the neural pathways.  

• Science: Water molecules diffuse more easily along white matter fibers (anisotropic diffusion) than in gray matter. DTI captures this movement to map neural connections.

Structural MRI (sMRI)  

• Procedure: A strong magnetic field and radiofrequency pulses align hydrogen protons in the body. As protons relax, they emit radio waves that are detected to create detailed images of brain structures.  

• Science: The MRI machine detects energy released by protons as they return to their normal alignment after being disturbed by radiofrequency pulses, producing high-resolution images of brain anatomy.

Single Neuron Recordings  

• Procedure: Microelectrodes are inserted into the brain to record the electrical activity of individual neurons during specific tasks or stimuli.  

• Science: Neurons communicate through action potentials (electrical signals). The microelectrode detects these spikes as neurons fire, allowing precise measurement of neuronal activity.

Hemispheric and Gender differences

Brain Lobes

• Frontal lobe: thinking, planning, problem solving, emotions, behavior control, decision making

• Temporal lobe: memory, understanding language, facial recognition, hearing, vision, speech, emotion

• Parietal lobe: perception, object classification, spelling, number knowledge, visuospatial processing

• Occipital lobe: vision, visual processing, color identification

• Cerebellum: gross and fine motor skills, hand-eye coordination, balance

• Brain Stem: regulates body temperature, heart rate, swallowing, breathing

Hemispheric Differences

• Left Brain: associated with logic, language, math, analytical thinking, linear processing

  • critical thinking

  • analytic thought

  • language and verbal

  • written math and communication

  • right body control

  • “male” because it has more androgen receptors

• Right Brain: associated with creativity, spatial awareness, intuition, holistic thinking 

  • pattern recognition/intuition

  • pattern memory for vision, sound, and 3D forms

  • left body control

  • “female” because it has more estrogen receptors

  • non-verbal

Male v. Female Brain

• Females

  • more multitasking, able to manage several information flows simultaneously

  • greater bihemispheric processing in both verbal and spatial processing

  • have thicker corpus callosum (which connects the brain hemispheres

  • women tend to link stimuli, information, and emotions together

  • geared slightly more towards language

  • larger frontal and temporal lobe volume (inc. broca and wernicke’s)

  • think more using white matter (nearly 10x more)

    • transmit signals from one region of the cerebrum to another

  • brain connections criss-crossed between left and right

  • larger hippocampus and deeper limbic system, allowing them to feel the full range and depth of the emotional spectrum

  • left amygdala activated upon feeling pain

    • left amygdala more associated with “internal functions”

  • activation of hippocampus more dominant on left side

    • explains why women use more verbal strategies in cognitive reasoning

  • more prone to mood disorders because male brains synthesize serotonin faster 

  • handle stress better since estrogen + oxytocin (released during stressful events) produces a calming effect 

  • too much estrogen can weaken performance of learned tasks and memory tasks

• Males

  • have bigger brain volume and bigger skulls 

  • stronger left hemisphere specialization for verbal processing

  • strong right hemisphere specialization for spatial processing

  • mostly use the left hemisphere

  • lower verbal ability

  • men tend to separate information, stimulus, and emotions mentally

  • geared slightly more towards math

  • much larger inferior parietal lobe

  • think more using gray matter (use nearly 7x more gray matter)

    • interprets and processes information

  • male brains wired front to back with few connections between hemispheres

  • right amygdala activated upon feeling pain

  • oxytocin + testosterone: makes men more aggressive when stressed

Commissural Fibres (AKA interhemispheric fibres)

• connect the identical cortical areas of the two cerebral hemispheres 

1. corpus callosum

   1. largest commissure

   2. connects two lobes of the cerebral cortex

2. anterior commissure

   1. crosses midline in upper part of lamina terminalis

   2. Posterior neocortical component

      1. large, interconnects the lower and anterior parts of the temporal lobe

   3. Anterior paleocortical component

      1. smaller, interconnects the olfactory regions of the two hemispheres

3. posterior commissure

   1. crosses midline through the inferior lamina of the stalk of pineal gland

4. hippocampal commissure (commissure of fornix)

   1. interconnects the crura of fornix of the two hemispheres, thus forming the hippocampal formation

5. habenular commissure

   1. crosses the midline through the superior lamina of the stalk of pineal gland

Sensation and Perception

• transduction: transforming signals into neural impulses

  • changing stimulation to sensation

  • info. goes from senses to the thalamus, then to various brain areas

• thresholds: boundaries of sensation signal detection theory

• sensory adaptation: decreased responsiveness to stimuli due to constant stimulation

• cocktail-party phenomenon: ability to focus one’s listening attention on a single talker among a mixture of conversations and background noise, ignoring other conversations

  • form of selective attention

• energy senses: detect physical energy like light (vision) or sound waves (hearing)

• chemical senses: detect molecules, like taste (gustation) and smell (olfaction), meaning they respond to chemical stimuli rather than energy waves

• vision: how the nervous system processes light

1. gathering light

   1. light enters through a narrow opening

      1. cornea: transparent eye cover

      2. iris: muscle, colored part of the eye

      3. pupil: opening in the iris that’s sensitive to light and emotion

2. within the eye

3. transduction

4. in the brain

   1. feature detectors: groups of neurons in the visual cortex that respond to different types of visual images

• color vision theories: explain our ability to distinguish between colors

  • trichromatic theory: three types of receptors (cones)

    • these three cones make millions of color combos

    • doesn’t explain afterimages or color blindness well

  • opponent-process theory: three types of bipolar receptors (black-wite, red-green, blue-yellow), supported by negative afterimages

    • if one color is stimulated, the other is inhibited

  • thought to work together:

    • trichromatic:cones

    • opponent-process:thalamus

• principles of visual perception

  • process used to organize sensory impressions is caused by the light that strikes our eyes

  • sensation is a mechanical process

  • perception is an active process

    • involves experiences, expectations, and motivations

• perception of motion

  • visual perception of motion is based on change of position relative to other objects

• constancy: acquired through experiences, creates stability

  • size, color, brightness, and shape constancy

• hearing: transduction in the ear

  • pitch theories

    • place theory: diff. hairs in the cochlea vibrate when they hear diff. pitches, so some hairs vibrate when they hear low pitches and others vibrate when they hear high pitched

  • frequency theories

    • the height of the wave gives us the amplitude of the sound

    • frequency of the wave gives us the pitch of the sound

  • conduction deafness is when something goes wrong with the sound and vibration on the way to the cochlea vs/ nerve (sensorineural deafness)

• touch; cutaneous senses: receptors located in our skin

• pain; gate control theory: sensations are mediated by neural gates in the spinal cord that allow them to continue to the brain

• taste

  • papillae: bumps on our tongue, is where taste buds are located

    • sweet, salty, sour, and bitter

• body position senses

  • vestibular: sense of balance; tells us where our body is oriented in space

    • located in our semicircular canals in our ears

  • kinesthetic sense: tells us where are body parts are

    • receptors located in our muscles and joints

Attention

• attention: selecting certain stimuli from many and focusing cognitive resources on those selected for further processing (in memory)

• filter theories

  • selective attention: ability to perceive a particular stimulus of interest while ignoring other stimuli

  • divided attention: two or more stimuli share cognitive resources

  • early selection: attentional filter that operates after sensory processing but prior to meaningful semantic processing

• attenuation: attentional filter that lowers the strength of the sensory signal on the unattended channel

• late selection: operates after meaningful semantic processing but prior to response preparation

  • all stimuli are recognized but are narrowed down to the most relevant during response preparation 

• capacity theory: attention is limited in overall capacity and that our ability to carry out simultaneous tasks depends on how much capacity the tasks require

• views attention as a mental effort; the more a task requires a limited pool of available capacity, the more mental effort a person exerts

  • mental effort increases as the proportion of available attentional capacity increases

    • can measure this through reaction time to a secondary task that competes for limited attentional capacity with a primary task

• multiple resources theories: ability to perform two tasks concurrently depends not only on their respective depands on capacity but also on specific resources required (e.g., perceptual vs. cognitive)

• C.D. Wickens three dimensions of resources

  • auditory vs. visual perceptual modalities

  • perceptual-cognitive resources vs. response resources

  • verbal vs. spatial processing codes

• automatic processes: require little, if any, mental effort and occur without intentional control, even when an individual attempts to stop it from happening

  • operate outside the scope of conscious awareness

  • processes develop automatically either through genetic programing or as the result of extensive practice

  • preattentive (processed before conscious attention is given to it)

    • posner and snyder categorized a process as automatic if it occurred

      • unintentionally

      • unconsciously

      • without depleting attentional resources

• controlled processes: intentional, conscious, and demanding of attention

  • demand extensive mental effort, require intentional control to operate, and enter conscious awareness

• visual attention

  • neural basis of selection: neurons in the occipital cortex act as feature detectors that are tuned to respond maximally to highly specific visual features, such as a line at a particular orientation

    • line must stimulate a specific area in the retina of the eye, which defines the receptive field for the neuron in question

    • receptive field, a group of cells in the retina, all map onto a specific neuron in the cortex that is ‘looking for’ the feature to which it is tuned

    • control of these changes in receptive fields lies in the thalamus, a structure deep in the midbrain that serves as a crossroad for an extremely large number of sensory pathways

• spatial neglect: disorder characterized by failure to attend to all areas of the visual field

  • people with right hemisphere damage will not see objects in the left visual field

• executive attention: supervisory attentional system that inhibits inappropriate mental representations or responses and activates appropriate ones

• important in planning, decision making, and other complex cognitive tasks

  • needed when

    • planning or making decisions

    • correcting errors

    • required response is novel or not well-learned

    • conditions are cognitively demanding or dangerous

    • an automatic response must be inhibited and overcome

• feature integration theory: states that automatic preattentive processing of features must be followed by controlled attentional processing to bind the features into a whole object

• inattentional blindness: superthreshold (very strong) stimulus that is directly fixated on for 200 milliseconds (a long leisurely glance when attention is, as usual, locked onto the fixation point, is simply not seen

  • without attention and the binding that it supports, perception fails

• attentional blink: interval of time after the target is presented when other stimuli in the series are not perceived

  • seems to be a refractory period following the encoding of the first stimulus that prevents attending to the second stimulus