The mind + brain, studying cognition (lec. 3) Flashcards
Assumptions of cognitive research
- Mental processes exist
- Mental processes can be studied scientifically (Need to use rigorous experimentation)
- We are active information processors (We are agents that manipulate information to produce behaviours + We do not only passively respond to information; Behaviourism)
- The basis of mental processes is the brain
Mindy-body problem
How are mental events related to the body (and the brain)?
- Dualism: the mind and brain are separate entities that are equally important
- Monism: the mind and brain are the same; Only one entity exists
Interactionism (dualism)
The mind and brain interact to induce events in each other: the mind can affect the body (ex. thinking alters brain chemistry) and the body can affect the mind (ex. hormones affect cognition). This subscribes to the idea that we have a “soul”. Cartesian dualism is a type of interactionism (Descartes thought that the pineal gland was the principal seat of the soul, where the interaction between entitles occured)
Epiphenomenalism (dualism)
- Mental thoughts (mind) are caused by physical events (brain), but thoughts do not affect physical events (1-way interaction)
- Mental events are like steam coming
off a train (Thomas Huxley). The steam (mind) doesn’t affect how the train (brain) works, even if it’s a separate entity
Monism
There is one basic entity that presents as both mental and physical responses. Types of monisms:
* Idealism: all reality is a mental construct, physical and mental
* Neutral Monism: the underlying nature is not mental or physical but something else, something neutral
* Materialism: all reality is the result of physical processes
Neurons vs. nerves vs. glial cells
- Neurons: Specialized cells that receive and transmit information
- Nerves: Bundle axons that carry information long distances between neurons
- Glial cells: Support cells for neurons (ex. hold neurons in place, protect and repair neurons)
CNS vs PNS
Central Nervous System (CNS)
o Brain and spinal cord
o Cognition primarily takes place here
o Voluntary actions
Peripheral Nervous System (PNS)
o Outside the brain and spinal cord
(body)
o Involuntary actions
The 2 are highly connected: the PNS informs the CNS about the environment and the CNS regulates the PNS response after interpretation of information
Subdivisions of PNS
Somatic Nervous System
* Signals from brain to end organs
* Voluntary control of muscle and senses (flexing muscles)
Autonomic Nervous System
* Up- and down-regulates involuntary bodily functions
* Digestion, respiration, hear rate
* Sympathetic and parasympathetic systems
* Control of physiological responses in different ways
Functional specialization: Phrenology
- Gall and Spurzheim (late 1700s)
- Parts of the brain correspond to mental functions and personality. Well-used mental functions -> related brain areas grow (bump), and under-used mental functions -> related brain areas shrink (dent)
- It is based on the false assumption that the highly developed functions have larger brain areas. It used speculation for localizing functions
Functional localization / specialization
Modern neuroscience identifies brain area or networks that supports a particular function, from neuropsychological cases and neuroimaging tools.
Example: Fusiform face area (FFA). Could be functional specialization, or this region can discriminate exemplars of any category someone has expertise (ex. greebles study)
Methods to study brain-behavior link
- Behavioral measurements:
* Behavioral experiments (voluntary responses). Demonstrated with early information processing experiments
* Psychophysiological measurements (involuntary responses) - Behavioral neuroscience methods:
* Animal models - Cognitive neuroscience methods:
* Patient cases
* Neuroimaging tools
Behaviour: Psychophysiological measurements
- Measure activity in the PNS in response to things that humans perceive or imagine (CNS)
- PNS influences CNS via connections
- Some examples : Eye movements, Body gestures, Skin conductance
Skin conductance measures emotion
Skin conducts electricity when it sweats. This happens when we are emotionally aroused. Devices can use electrical conduction as an indirect measure of emotional arousal. This is an autonomic response but can affect voluntary actions (ex. response to threat and fear when doing something). It relates to brain activity
Skin conductance and PTSD
There is an altered skin conductance response in anxiety disorder patients (including PTSD). There was a study done with three participant groups: Veterans with PTSD, Veterans without PTSD (NC), Control Participants (CC). They istened to white noise and combat sounds. Researchers found higher skin conductance in people with PTSD
Behavioral neuroscience methods: Animal models
Investigating neural underpinnings of actions (not cognition), typically with animal models
- Strength: Provides a causal link between brain and behavior
Weaknesses: Doesn’t tell us about human cognition (ex. autobiographical memory) + Differences in brain structure and function across species puts limits on the generalization of these findings
Animal models: Lesions. Example question “Is the hippocampus important for spatial memory?”
Hippocampal lesions in one group of rats and not another group (intact)
* Measure the ability of these rats to do navigate a learned maze or route (e.g., find platform in water tank - Morris water maze task)
* Hippocampal lesion rats cannot do this thus
hippocampus is important for memory
Cognitive Neuroscience: Patient (Neuropsychological) cases
Study brain function by comparing the behavior of brain- injured patients to healthy control participants. If brain injury to area X leads to impairment on specific cognitive function, then that brain area must support that function. This follows ideas of functional specialization.
Example: split-brain patients led us to know more about the brain’s 2 hemispheres.
Corpus callosum
The connection between the two hemispheres
* When cut, brain hemispheres cannot communicate with each other
* In these cases, we can study the separate contributions of each hemisphere to cognitive tasks
Split brain patients
Research on split brain patients examined processing differences between the two hemispheres of the brain. FIndings:
* The left hemisphere supports speech and language
* The right hemisphere supports visual-spatial processing
Split brain cases: The classic findings
- Left hemisphere supports speech and language - processing. Without communication, information to the right visual field (left hemisphere) can be verbally named and described in words
- Right hemisphere supports visual-spatial
processing. Without communication, information to left visual field (right hemisphere) cannot be described verbally but can be expressed via visuo-spatial processes
Implications of split-brain patient studies
- No ‘module’ is damaged in these case. Connections between brain regions are just as important as the operations. The brain isn’t like a computer – it is a network of interconnected computers.
- It raises the idea of dual consciousness:
“It is customary to think of a human being as having a single brain, possessing a unitary mind, constituting a unique individual person. However recent studies of patients whose cerebral commissures have been sectioned to prevent interhemispheric spread of epileptic seizures suggest a very different state of affairs.” (Roland Puccetti, 1973)
Cognitive Neuroscience: Neuroimaging techniques
Examine change in neuronal communication that give rise to mental functions. EEG, fMRI, Brain stimulation techniques…
Electroencephalography (EEG)
An active brain produces electrical
activity: event-related potentials (ERP) show activity related to behaviors and contexts. EEGs measure activity in a large group of neurons a a certain time. It provides a great estimate of when the brain is active (good timing, millisecond level). However, lots of things can affect ERP signals, low spatial resolution, must collect a lot of experimental trials.
Types of MRI
- Structural MRI: Anatomy of the brain (ex. volume, location of grey matter), used to detect structural anomalities
- Functional (f)MRI: Information about activity in the brain. An indirect measure as it measures blood flow and not neural activity
fMRI functioning
Active brain areas need oxgen (metabolic energy). A magnet detects changes in oxygenated blood.
It is a measure of the ratio of oxygenated and de-oxygenated blood flow in regions of the brain during a task. This measurement is then used to create a spatial image of brain activity.
Examples of fMRI findings
- Right lateral occipitotemporal cortex: cortical selective region for processing body parts
- Parahippocampal place area: Recognizing or thinking about scenes/spatial layouts
- Supplementary motor cortex: Performing or imagining motor movements
fMRI strengths vs. weaknesses
Strengths:
* Provides good spatial resolution
* About a 1000 papers per month ( lots of replication, validation)
Weaknesses:
* Does not provide good temporal resolution
* Indirect measure of neural activity (there is the assumption that increase in blood flow means more activity)
* It is very noisy
Brain stimulation
Noninvasive method of changing brain activity that can inhibit or increase activity. A main form is Transcranial Magnetic Stimulation (TMS) in a focal magnetic field induces temporary change in brain activity. A study showed that participants subjected to TMS group had improved scores (up to 25%) on post-training compared to pre-training memory tests
TMS, pros and cons
- Good to test causality (testing effect of temporary lesion or stimulation). In comparison, fMRI and EEG are correlational (associate brain activity to task)
- Stimulation techniques have broad effects on the brain, so it is hard to localize effects
- The way it works is not entirely clear
Questions and thoughts on studying cognition
- If the brain supports thoughts, can we have free will? Free will cannot require the idea that a thought exist before it exists (i.e., reflected in the brain)
- What are the implications of taking a strict one-to-one functional specialization view?
- How much do our methods determine the questions we ask in research?
