The probing excitability approach which tests the responsiveness of the motor system during a cognitive task. If the motor cortex is required for a cognitive task then it should already be activated when single-pulse TMS is delivered. The measure of interest is how strongly the motor cortex reacts to the pulse itself and how strongly the body part will move in response to the additional stimulation.
The paired pulse approach first activates the brain using a sub-threshold stimulation and then interferes with neuronal transmission using a second supra-threshold stimulation and aims to answer the question of how strongly the first stimulation affects the second.
Schizophrenics have an increased Cortical Silencing Period (CSP), meaning that the cooling off period is reduced after excitation and thus there is hyperexcitability and problems with getting rid of muscular activation.
The virtual lesion approach involves repeated TMS (rTMS) which can inhibit functions for a longer period of time.
The Z distribution uses the population SD
The t statistic takes into account both the expected mean and a measure of the standard error of the mean based on the sample
The bottom of the above equation refers to the standard mean of the population
The x value with a hat refers to the sample mean
Great temporal resolution but poor spatial resolution
Can't test causality
Electrode cap signals are amplified and EEG is recorded during experimental stimulation
EEG reflects post-synaptic potentials (voltages that arise when NT bind to receptors of the post-synaptic cell). This causes ion channels to open/close, leading to graded change sin the potential across the membrane.
EEGs pick up the summation of charges
Folding within the brain (gyrus) destroy signals, therefore there is not an accurate representation
Signal is band-pass filtered to remove low (<.5-1Hz) and high frequencies (>35-70Hz) because they do not reflect brain activity
EEG is biased to signals generated in superficial layers of cerebral cortex
The meninges, CSF and skull make it difficult to localise the source
The inverse problem: you can reconstruct scalp configurations if sources are known, but you cannot reconstruct the source if the scalp configuration is known
A) Artefact rejection and occular correction must occur in order to clean the raw signal
B) The signal is unaffected by sweating and electrical noise
C) Mathematical algorithms remove most of the noise and artefacts but cannot remove the noise generated from muscle clenching
D) Event related potentials involve multiple trials
A and D
B and D
MRI is utilised in reverse inference of cognitive processes based off the presence of activation
A magnetic field of 3T is usually used for functional imaging
Magnetisation on the z-axis is easily measured because the movement is in the same direction as the magnetic current from the MRI
The head coil is used to send and receive radio frequency pulses
The Hydrogen protons precess either parallel of antiparallel and the precession frequency of protons depends on the strength of the magnetic field.
Phase coherence occurs when the protons are all doing the same thing
A radiofrequency (RF) pulse is applied perpendicular to the magnetic field which matches the precession frequency of the protons and is thus absorbed.
The RF pulse has two effects: 1) it tilts the magnetisation vector to the transverse plane and 2) it aligns the precession of the spins which means that the protons' rotations are "in phase". The transversely rotating magnetisation vector can then be recorded as a signal.
When the RF pulse is switched off the longitudinal magnetisation decays and the transversal magnetisation is re-established. This is known as the "relaxation" phase
The transversal magnetisation decays with different speeds depending on the tissue as a result of the differing density of protons, as they lose coherence because they will be influenced by other protons in their environment.
The signals from different protons will get out of phase with each other and begin to cancel each other out
Resonance means that protons will only absorb the RF that matches their precession frequency. By allowing the magnetic field to vary linearly, we can cause the resonance frequency to vary throughout the brain, this can be achieved using gradients.
1) divide the brain into slices and use a slice selecting gradient through the gradation of the RF pulse. 2) form a phase encoding gradient gives us the y axis coordinate. 3) frequency encoding gradient gives us the x axis coordinate
Fourier transformation allows for the measurement and reconstruction of the 3D brain, but takes just under 1 second
Deoxygenated blood increased the signal (it is paramagnetic)
Neural activity is accompanied by a local oversupply in oxygenated and therefore provides a better BOLD signal
You can track which brain regions are active during cognitive tasks through oxygen levels
There is a temporal lag in the bold response (8 secs - haemodynamic response function) and the BOLD signal requires 16 secs to restore to baseline
High blood flow may mean relatively less oxygen is extracted
It is not valid to compare signals between different regions as the signal change is different
Excitation inhibition networks (EIN) are small and highly interconnected functional microunits. If they equal 0 it means the excitatory neurons and inhibitory neurons have cancelled each other out, and thus are not observed in the BOLD signal.
FMRI displays brain activities as blobs of activation, but for the most part the brain is not modular
Although we interpret the results of fMRI correctly it us not clear whether we have not accounted for extraneous variables
Temporal resolution is poor and spatial resolution is limited by the relatively large size of a voxel, which may contain up to 100,000 neurons
There is a multiple comparison meaning that a bonferroni correction must be made by dividing the alpha level by the number of t tests (50,000)
FMRI has been utilised to confirm how the human visual system represents information and how the visual content becomes available to higher level visual areas in the cortex
Kanwisher and colleagues (1997) discovered that the fusiform gyrus responded strongly to faces, indicating that the visual areas of the brain are modular
It would be simply impossible if the brain had modules for everything
Kanwisher and colleagues (2002) suggested that the visual system might not be organised by specific object categories, rather it may be organised by where we encounter things in our visual field
Malach and colleagues (2002) argued that coding is driven by resolution needs and the fusiform face area is good for everything that requires high resolution
Gauthier and colleagues (1999) discovered that the the FFA responded strongly to greebles indicating that it is a specialised area for expertise rather than a modular area for faces
Reverse inference is a problem because: task A shows that brain region Z is active in this study. In other studies, cognitive process X is occurring when brain region Z is active. Therefore, in this study activity in brain region Z means that there is engagement of cognitive function X.
Brain region Z may not be exclusively used in cognitive function X, it may be active in other tasks.
Some researchers suggest that anterior regions of the brain is associated with abstract information and is more diffuse and harder to map, as compared to the posterior regions which represent more specific content
The frontal lobe may be recruited more strongly during more difficult tasks
A lot of brain regions are a part of a "multiple demand" network. This means that if we see activation of one of these, we still do not know what each individual brain region is responsible for
If the brain region is activated by many cognitive functions we learn very little about it, however, if the experimental setup succeeds in manipulating the cognitive process of interest, it can still provide useful information about the process
Only a few neurons in a voxel may be showing differences which can only be detected through more sensitive tasks.
The quality of the task to measure the cognitive process
When the null hypothesis is accepted we don't know the significance because statistic tests are designed to make the alternative hypothesis difficult, not the null hypothesis, therefore we cannot interpret the null hypothesis results
The specificity of region for this cognitive process
Epileptic seizures arise from sudden excitation in groups of neurons with a loss of inhibitory potential
Intermittent derangement of the nervous system presumably due to a sudden, excessive, disorderly discharge of cerebral neurons
Temporal lobe epilepsy involves recurrent unprovoked seizures originating from medial or lateral areas of the temporal lobe
Simple partial seizures (with loss of awareness/consciousness) and complete partial seizures (no loss of awareness/consciousness)
Surgical removal of the lesioned hippocampus can't cure, but can reduce the number of seizures.
The most common pathophysiology of TLE is hippocampal sclerosis and results from neuronal loss and gliosis
Partial seizures often originate from a particular past of the brain and often spread to the whole brain.
Often occurs early in life (2 years plus)
Other aetiologies include past infections, tumours and vascular malformations
The temporal lobe includes the superior temporal gyrus, middle temporal gyrus and inferior temporal gyrus
He was having 10-20 major seizures per day due to bilateral hippocampi sclerosis and thus had both hippocampi removed
HM struggled with procedural memory, however, his declarative memory came back over time.
After his surgery he had fewer seizures, a normal IQ, a normal attention span and retrograde and anterograde amnesia
Retrograde amnesia leads to an impairment in one's ability to recall memories prior to an event, whilst anterograde amnesia leads to an impairment in creating new memories after an injury
Intact memory function relies on a neuroanatomical network, involving functional asymetry many brain regions including the temporal lobes which are the engine of memory
Medial temporal lobe structures are essential for memory
Medial temporal structures are more essential for anterograde memory
There is a distinction between declarative and procedural memory
The hippocampus was the region of the brain first identified to support memory and the hippocampal formation includes the dentate gyrus, CA1-CA3 and the subiculum
Patients have material-specific memory deficits related to involved medial temporal lobe (MTL)
Left MTL lesion results in verbal memory impairment whilst right MTL lesion results in non-verbal/visual memory impairments
The hippocampus is also known as Cornu ammonis and can be labelled CA1 to CA5
They are all correct
The above image is a schematic representation of the Medial Temporal Lobe
Information is integrated in sensory systems and is sent to the hippocampal formation for long term storage
Memories can be accessed by reciprocal connections between the hippocampal formation and the temporal neocortex
The subcortex is part of the limbic system and is involved in higher order thinking. (sensory perception, generation of motor commands, spatial reasoning, conscious thought and in humans, language)
The hippocampal formation and surrounding structures are essential for learning and consolidating novel information.
The consolidation theory suggests that after a period of consolidation, information may be retrieved independent of involvement from the hippocampal formation
The multiple trace theory suggests that autobiographical/episodic experiences always require the hippocampal formation
The hippocampal formation is not necessary in relational memories between two arbitrary pieces of information.
Information must move through the hippocampal formation and surrounding structures for learning to occur, thus the hippocampal formation in the MTL are fundamental structures of declarative memory
Papez's circuit, frontal lobes and the diencephalon are all involved in memory
Papez's circuit and the amygdala form the limbic system which is integral in emotional memory formation
Regardless of the strength of an emotional experience the storing of the memory is always the same
Lesions of the limbic system result in a loss of conditioned fear, an impairment of fear learning and reduced memory for emotionally laden events
Papez's circuit is comprised of mamillary bodies (part of the hypothalamus), fornix, anterior thalamic nuclei, cingulate gyrus and the hypothalamas
Declarative memory impairment is least reliable when the hippocampus or the Anterior Thalamic Nuclei are lesioned
Lesions to Papez's circuit result in declarative memory impairment (poor relational memory/encoding)
The frontal lobe is involved in developing and implementing strategies for appropriate memory, encoding and retrieval
Dorsal Lateral Pre-Frontal cortex damage results in an impairment in remembering contextual detail i.e. the source of information, the chronological order of memories can result in confabulation (the production of statements involving bizaar distortions of memory)
There are a lot of connections withing the pre-frontal cortex that go to the peririhinal cortex
Diencephalon means interbrain and is comprised of the thalamus and the hypothalamus
The thalamus is connected to all regions of the brain and damage to a specific location will mean damage to a connection of a specific brain region and the damage results in the same problem as would occur id that brain region itself was damaged
Anterior and medial lesions are more likely to cause memory deficits than posterior or lateral lesions. This is because parts of the thalamus have a direct connection to the temporal lobe
Dense amnesic syndrome is associated with damage to the mammillo-thalamic tract, as it connects to the posterior thalamus and hippocampus
If the Medio Dorsal Nucleus and or the Internal Medullary Lamina is damaged but the MTT is spared, then there will be specific retrieval difficulties but preserved recognition
They are all correct
Dorsal Medial Thalamus damage results in deficits in selecting the appropriate information to be retrieved (active retrieval) due to reduced mental flexibility, whilst damage to the intralaminar results in deficits seen in semantic memory and memory retrieval
Lesions of the frontal lobe lead to impaired abilities to organise the encoding, retrieval and maintenance of memories
Learning involves synaptic plasticity which refers to the biochemistry of synapses changing, thus altering the effects on the post-synaptic neuron
Long term potention refers to a long term increase in the excitability of a neuron in response to a a particular synaptic input , caused by repeated high frequency of that input
None of them are incorrect
Hebb's rule referes to growth processes and metabolic changes which occur in a pre-synaptic and post-synaptic neuron in order to increase the efficiency of firing in the post-synaptic neuron
LTP occurs in the hippocampus (particularly CA5 and the dentate gyrus, but also in the entorhinal cortex) and in the prefrontal cortex, the motor cortex, thalamus, amygdala and visual cortex
LTP causes more glutamate receptors to be inserted in the post-synaptic neuron, more glutamate to be released and bushier dendrites
Sensitization refers to a single noxious stimuli causing an exaggerated synaptic response to repeat presentation of the noxious stimulus
Long term depression is resultant of low frequency stimulation at synapses and can decrease synaptic strength
Habituation refers to the process in which repeated stimulation reduces the strength of the synaptic response and thus reduces neurotransmitter
They're all correct