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CLPS 450 Study Guide - Summary Brain Damage And The Mind (Formerly Psyc 0470)
Brain Damage And The Mind (Formerly Psyc 0470) (CLPS 0400)
Brown University
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Introduction
- What distinguishes the field of cognitive neuropsychology from that of classical neuropsychology and clinical neuropsychology? How does it relate to the field of cognitive psychology?
- Branch of Cognitive Psychology
- Science of understanding the nature of mental processes
- Distinct from Classical Neuropsychology
- NOT simply inferring function of brain regions from pattern of behavioral abilities
- Distinct from Clinical Neuropsychology
- NOT necessarily concerned with treatment or rehabilitation
- What are the aims of cognitive neuropsychology?
- Explain patterns of impaired & intact performance of patient populations in terms of damage to one or more components within a cognitive model
- Draw conclusions about normal cognitive processes from this pattern of performance
● Compare the advantages and disadvantages to the use of brain-damaged patients vs. healthy normal subjects for understanding normal cognitive processes? ● What factors contribute to the behavioral performance of a patient? ● How do these factors influence our conclusions about the underlying cognitive processes? Advantages of studying patient populations :
1. Effects are often robust & sometimes counterintuitive,
2. Can direct you to the important aspects of cognition to study
Disadvantages:
1. Want to draw conclusion about a disrupted cognitive process or mechanism of interest,
but also have to contend with...
Individual variation in performance
Effects of compensatory operations
Effects from disruption of other processes
- What is the mind-body problem and what frameworks have been proposed to “solve” it?
How can a physical substance (brain/body) give rise to mental experiences? Dualism (e., Descartes): ● The mind and brain are made of different substances, though they may interact ● The mind is non-physical and immortal, the opposite of the body ● They interact in the pineal gland ● The stimulations of the sensory organs cause vibrations that are picked up by the pineal gland, which creates a non-physical sense of awareness Dual-aspect theory (e., similar to wave-particle duality) ● Proposed by Spinoza ● Mind and brain are two different levels of explanation for the same thing Reductionism ● Although cognitive, mind-based concepts are currently useful for scientific exploration, they will be replaced by biological constructs eventually ● All behavior can be explained through physiological events in the brain ● Psychology will eventually reduce to biology as we learn more about the brain
- What is functional specialization? How were Gall’s and Penfield’s examples of functional specializations different? How do Broca’s and Wernicke’s observations of aphasic patients relate to the notion of functional specialization? ● Functional specialization: Different regions of the brain are specialized for different functions ● Gall advocated for phrenology : the failed idea that individual differences in cognition can be mapped on to differences in the skull shape. It made two assumptions: 1. Different regions of the brain perform different functions and are associated with different behaviors and 2. The size of these regions produce distortions in the skull and correlate with individual differences in cognition and personality ● Penfield and his workers took functional specialization forward, but were empirically derived unlike phrenology. They weren't constrained by cognitive theories, either. Broca (1861): ● Broca reported the brain damage of two patients: Tan (called so because he could only produce few words, including Tan ) and Leelong. He found that only language was damaged but other functions remained intact. He concluded that language must be localized to a part of the brain Wernicke (1874): ● Subsequent studies argued that language could be further subdivided into speech recognition, speech production, and conceptual knowledge was motivated by the observation that brain damage could produce a double dissociation between production and comprehension suggested at least two speech faculties in the brain that could be impaired individually. ● Wernicke also came up with the model of conduction aphasia based on the observation of patients that had: Poor comprehension Fluent speech Poor repetition This allowed us to produce models of language ○ Sensory center ○ Motor center ○ Must be a transmission pathway between the two ○ Damage to motor area produces patient like broca’s
○ Interrupts functioning of the brain in the region of interest by sending a magnetic pulse to that region ○ Coil contains a wire carrying an electric current ○ A rapid change in the current creates a magnetic field ○ The magnetic field induces a current in the nearby neurons (causing them to "fire", i. generate action potentials) ○ This disrupts the cognitive function that they may be doing at that point in time (à virtual lesion) The TMS pulse directly alters neural activity in a spherical area of approximately 1 cm 3 . ○ Summary: ○ Coil placed over target brain region ○ Cognitive failures recorded ○ Interrupts functioning of the brain in the region of interest by sending a magnetic pulse to that region ● · TMS brain stimulation is relatively mild. ● · Many natural situations stimulate the brain (e., drinking a cup of coffee) ● · Not used on people with epilepsy ● · Number and rate of pulses is regulated by ethics guidelines ● · Some suggestion of beneficial effects ● · (e., in depression) ● THE GREATER THE RATE OF CHANGE IN ELECTRIC CURRENT, THE GREATER THE MAGNETIC FIELD - Faraday ●
- Transcranial Direct Current Stimulation) tDCS ● Stimulation ● Non-invasive ● Electric ○ Uses a very weak electric current ○ Cathodal tDCS: Decreases cortical excitability and decreases performance (Excitatory neurotransmitter) ○ Anodal tDCS: Increases cortical excitability and increases performance, GABA (Inhibitory neurotransmitter) ○ Period of stimulation = 10 minutes ○ Immediate effects are on resting membrane potential ○ After-effects: due to synaptic plasticity; influencing learning and neurotransmitter systems ○ Very little discomfort; maybe irritability if a small electrode is used
○ Used for cognitive enhancement and neurorehabilitation (the latter is for damaged brains)
3. Electrophysiological methods: EEG
(Electroencephalography)/ERP(Event-Related Potential)
● Recording
● Non-invasive
● Electrical
4. and Single-cell
● Recording
● Invasive
● Electrical
5. Magnetophysical methods (MEG or Magnetoencephalography)
● Recording
● Non-invasive
● Magnetic
- Functional imaging methods: HEMODYNAMIC- PET ● Recording ● Invasive ● Hemodynamic
- andfMRI: Record physiological changes associated with blood supply to the brain, which evolve more slowly over time. ● Recording ● Non-invasive ● Hemodynamic
A. Temporal resolution: the accuracy with which one can measure when an event is occurring Eg: EEG, MEG, TMS, and single-cell recording have ms resolution fMRI has a span of several seconds. B. Spatial resolution: the accuracy with which one can measure where an event is occurring Eg: Lesion and functional imaging methods can go to the mm level Single-cell recording is at neuronal level, but involves operating on the brain itself and is only performed on animals C. Invasiveness: Whether the equipment is located internally or externally. Eg- PET is invasive because it requires an isotope injection. 6. Explain why cognitive neuroscience (and cognitive neuropsychology in particular) is not simply a modern version of Gall’s phrenology? ● Backed up by empirical support which could be tested and falsified ● Developing models of cognition that did not make direct reference to the brain ● Cognitive neuropsychology is the approach of using patients with acquired b rain damage to inform theories of normal cognition
Describe the arguments as to why the discipline of cognitive psychology needs neuroscience and vice versa. (see textbook & last sections of Feinberg & Farah article)
Connectionist modeling: Computational models in which information processing occurs using many interconnected nodes, which are the basic units of neural network models and are activated in response to activity in other parts of the network.
Interactivity: Later stages of processing can begin before earlier stages are complete.
Modularity: The notion that certain cognitive processes/regions of the brain are restricted in the type of information they process.
Domain-specificity: The notion that a cognitive process/region of the brain is dedicated solel y to one particular type of information.
Historical Perspective
- How did the approach to understanding mental activity change across each time period (Classical Antiquity through Modern Times) and what factors contributed to those changes?
Who were the major players in each period and in what ways did they advance (or set us back) our understanding of the mind? Classical Antiquity Period: ● Early anatomists believed ventricles critical ● Cortex was often schematically drawn or misrepresented like intestines until the 18th century
Heart/Diaphragm vs. the Brain Alcmaeon (450 BC): one of the earliest to practice anatomical dissections as a method of understanding the brain Hippocrates (425 BC): author of the essay “ Sacred Disease ” in which he discusses the causes of epilepsy Aristotle (384 BC): maintained the cardiocentric view; limited to animal dissections Herophilius (270 BC) &Erasistratus (260 BC): provide the 1 st detailed descriptions of the ventricular system Galen (129-199 BC): ascribed to the view of 3 components of cognition, but would not localize the functions
- Expanded on Aristotle’s idea of humors
- The body is composed of a balance between the four elements present on earth: fire, earth, water & air. These elements were manifested in the body as: yellow bile (choler), black bile (melancholy), blood, and phelgm.
- Ascribed to the idea of “psychic pneuma” Vital spirits formed in the heart and were pumped to the brain, where they mixed with pneuma (air found in the cavities of the brain)
- This model held sway for 1500 years
Localization of the Soul Medieval Period The Cell Doctrine: Ventricular localization
- Three-part model Perception (anterior) Reason (middle) Memory (posterior)
- Traced back to Syrian Bishop Nemesius (born 340 AD) & St. Augustine (354-430 AD)
- Cognitive functions are the product of the non-corporeal soul
- Tripartite conception of the soul
Transitional or Renaissance Period ● Versalius (more detailed depictions of the cerebral cortex) and Willis (role of cortex in cogni tive function) ● More detailed depictions of the cerebral cortex · Descartes and Spinoza Localism/Holism Gall (phrenology) vs. Flourens
Emergence of Modern Cognitive Neuropsychology
- What is the cell doctrine? What are the links between neural structures and cognitive processes in this view? Why are Versalius and Willis important figures in the transition f rom ventricular- to cortical-based theories of brain function? Three-part model · Perception (anterior) · Reason (middle) · Memory (posterior) · Traced back to Syrian Bishop Nemesius (born 340 AD) & St. Augustine (354-430 AD) · Cognitive functions are the product of the non-corporeal soul · Tripartite conception of the soul
● Versalius ○ Agreed with Galen that convolutions don’t mean intelligence ○ BUT provides super detailed images of cortex for the first time. Before him, they were drawn as intestines.
● Willis ○ Uses anatomy to argue for the specific role of the cerebral cortex in intellectual ability ○ Rejected ventricular system idea ○ BUT carried over the three-region system ○ Introduced terms like hemispheres, corpus callosum, etc. ○ Talked about the fornix Shift came largely from COMPARATIVE ANATOMY studies
What is phrenology? Why did Gall's functional specialization approach fall out of favor in the scientific community? How is this approach different from that of fMRI studies in modern times? SEE PREVIOUS SECTION
Describe the model of Lichtheim. What was novel about the approach of the diagram makers to understanding the cognitive function of brain-damaged patients? In the context of this model, how did the diagram makers explain a variety of language syndromes exhibited by different types of patients (e., Broca’s aphasia)?
Wernicke came up with this after seeing the symptoms of his patients and how they differed from Broca's:
Lichtheim elaborated:
★ This led to models of cognition that don’t make direct reference to the brain, e., the information-processing models popular from the 1950s onwards ★ The models were inspired by thinking of the mind as a series of routines, like those found in computers
- What are the complementary strengths and weakness of patient-based and functional imaging methodological approaches to understanding the mental activity? ( see Ch4 textbook reading & last sections of Feinberg & Farah article)
DISADVANTAGES OF LESIONS OVER FUNCTIONAL IMAGING ● Lesion studies are not powerful enough to detect the importance of a region ● Impaired performance after lesion could reflect damage to tracts passing through the region as opposed to the region itself ● Lesions cannot be moved from different regions- functional imaging can see the entire brain at once ● Functional imaging offers better spatial resolution ● It also allows the study of normal brains rather than patients ● For some conditions, more than others, there may be reason to suspect reorganization- which only imaging can reveal
DISADVANTAGES OF FUNCTIONAL IMAGING OVER LESIONS
● The activated region could simply denote a different strategy being used by a patient- the area is not necessary for a certain function ● An activated region could just be used for general cognitive resources ● The activated region could be inhibited rather than activated ● If the baseline task is not chosen well, cognitive subtraction could result in an artificial null ● It is hard to detect activity in extremely small brain regions ● Functional imaging only reveals correlation, not causation. Meanwhile, brain damage is a natural experiment.
Methodological Approach
- Define each of the underlying assumptions of cognitive neuropsychology (i., Caramazza). What are the consequences if any of these assumptions are false? Do you think that these assumptions differ from that used by cognitive neuroscience or cognitive psychology? Why or why not? -Modularity or fractionation (Functional vs. Anatomical Structure) Fodor’s Properties Information encapsulation (each module can operate independently), domain specificity, mandatory operations (each operation must occur and cannot be restricted by cognitive beliefs), innate Neurological specificity
Universality All individuals share the same cognitive system Effects of lesions are stronger than individual variation
Transparency (Subtractivity) Performance reflects the total cognitive system minus those subcomponents (or connections) which have been affected by the lesion Lesion cannot create new modules New strategies can develop, but they must use pre-existing structures
Modularity false? Won’t see patients with highly selective cognitive disorders Universality false? Patient A’s data would suggest one architecture & Patient B’s data would suggest a completely different one Transparency false? Architectures inferred from patient data would not be successfully applied to data from cognitive psychology Cognitive neuropsychology looks primarily at impaired patients.
- Experts suggest that fractionation may depend on neural architecture. Nevertheless, we can observe selective deficits- even if some may be hard to uncover due to atypical neural architecture.
- The transparency assumption is the most problematic. Basically, one needs to assume that brain damage removes one component of cognition, but does not create a new one from scratch that is different or rearranged. However, it could be that the preexisting model has just been reinstated. Plasticity is pervasive at the neural level, and need not result in a behavioural change. Further, the transparency assumption refers to the organization of the cognitive system and not necessarily its location .This would not violate the assumption.
- The universality assumption could also be problematic- but Caramazza argues that this is the case for any method. Furthermore, individual differences are just noise when extrapolating to a general cognitive framework.
○ Therefore, the cognitive profile of each patient needs to be assessed separately from other patients ○ Argument is not against testing more than one patient, but this becomes a series of single case studies and not necessarily a group study (in that the patient data are combined to a group average) ● Conclusion: good for establishing different cognitive profiles, less good for linking cognition with brain structures
- What are the different ways of grouping patients? What conditions/research questions would lead you to use one grouping method over another?
Syndrome ○ Useful for investigating the neural correlates of a disease pathology, not for dissecting a cognitive theory Behavioral Symptom ○ Can potentially identify multiple regions implicated in a behavior Lesion Location ○ Useful for testing predictions derived from functional imaging
Selective lesion methods in animals are often used in behavioral neuroscience to understand the functions of the brain (described in textbook). What advantages do these types of studies have over patient studies? What are some limitations of these types of studies? Pros: 1. Possible to carry out far more selective lesions 2. Can use single-cell recording 3. Unlike human lesions, each animal can serve as its own control before and after the lesion. There can also be groups of such animals. 4. Cons: (other than the fact that you just killed a dog, you sick fuck) 1. Concerns for the welfare of the animals 2. Scientists working with the species must provide a justification as to why the research requires primates rather than other animals if using primates, or other methods. They also have to justify the number of animals they are using. 3. It is important to have careful breeding programs to avoid having to catch animals in the wild and to protect them from virurses. 4. It is important to give them adequate space and social contact.
There are some human traits that do not have obvious counterparts in other species, the most obvious one being language.
Describe how TMS creates virtual lesions. What are some of the practical issues/questions associated with using this methodology? What are its advantages/disadvantages over organic brain damage studies? SEE PREVIOUS SECTIONS
ORGANIC LESIONS ● Subcortical lesions can be studied ● Lesions can be accurately localized with MRI ○ Effects of TMS are less well understood spatially ● Changes in behavior/cognition are more apparent
TMS
● Temporary effects, so no brain reorganization ○ Reversible nature means that “lesion” can be moved across brain within subjects ○ Effects are focal AND can be moved within the participant ○ But can’t stimulate all regions of the brain ● Effects are brief ○ Can investigate the time course of cognitive process ○ Can investigate functional integration
PRACTICAL ASPECTS OF TMS: ● To use one pulse or many? When? (This depends on the nature of the task. Is time an independent variable?) ● How do we hit the right spot? (Define positions according to landmarks. You can use MRI/fMRI to locate regions, known as frameless stereotaxy) ● What is the appropriate control? (Use TMS pulse in a non-critical region: this is better than a sham pulse or no pulse, because it means the peripheral effects of the TMS can be minimized.)
Key Terms:
- Independent variable: Variable being manipulated by experimenter to determine a cause-effect relationship in an experiment
- Dependent variable: Variable being measured by experimenter to determine effect of dependent variable in an experiment
- Repetitive pulse TMS: rTMS: A train of pulses
- Single pulse TMS: One pulse TMS
- Split-brain: A surgical procedure in which fibers of the corpus callosum are severed
- Syndrome: A cluster of symptoms that are supposed to be related in some meaningful way
- Diaschisis: A discrete brain lesion can disrupt the functioning of distant brain regions that ar e structurally intact.
- Functional integration: The way in which different regions communicate with each other.
Hypothalamus: Concerned with body regulation: temperature, hunger, thirst, sexual activity, endocrine activity, etc. 4. In a coronal section of the cerebral cortex, there is a outer grey layer and a deeper larger white layer. What are these layers? What is the corpus callosum and what function does it serve? ● Gray matter and white matter. The different layers reflect the grouping of different cell types. Different parts of the cortex have different densities of each layer. Most of the cortex contains six main layers, termed neocortex. Other regions include the mesocortex and allocortex. ● The corpus callosum is a hard network of fibers, or a white matter tract, joining the two cerebral hemispheres. Its role is to relay information between them. 5. Briefly describe the particular cognitive functions associated with each lobe of the cerebrum.
Frontal lobe- motor area Parietal- somatosensory strip Temporal- Medial (memory), Lateral (auditory/verbal) Occipital - Vision
- How is the brain topographically organized at different levels (areas of the brain, projections across areas, laminar structure)? Describe the topographical features of the somatosensory and motor strips. Why do they differ? How is the brain’s organization both parallel and serial?
Areas of the brain:
Laminar organization: ● Stratified into six layers in the neocortex Profile distinct across different areas e., motor vs. sensory cortex Functional significance Distinct levels project to other distinct areas Brodmann areas
Somatosensory versus motor: The sensory homunculus depicts what parts of our body are most sensitive
(sensory wise)
These regions are organized differently since certain parts need to be more responsive to either touch/motor instructions. The more nerves dedicated to the area- the more the sensitivity.
CLPS 450 Study Guide - Summary Brain Damage And The Mind (Formerly Psyc 0470)
Course: Brain Damage And The Mind (Formerly Psyc 0470) (CLPS 0400)
University: Brown University
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