How to study the brain Flashcards
What are the (7) main methods of psychological study?
- Experimental ablation using kainic acid or RF current (combined with behavioural studies to determine brain function), followed by histological methods (slice and examine brain!)
- Study of humans with brain damage (e.g. HM)
- Electrophysiology - microelectrodes can be used to record single-unit APs and macroelectrodes for areas, also EEGs and magnetoencephalography.
- Imaging (MRI and PET)
- Mild electrical stimulation
- Computational models/brain-based devices
- Neurochemical methods
What happened to HM?
His medial temporal lobe was surgically resected (to improve epileptic seizures) and he became unable to form new declarative memories, as shown by behavioural and cognitive analysis.
How are lesions experimentally induced and how else is the brain manipulated?
- Selective destruction of specific brain sites (mechanic, electrolytic, neurotoxic)
- Stereotaxic surgery
- Electric stimulation of brain sites
- Targeted mutations of brain-specific genes
- Optogenetics
- Trans-cranial magnetic stimulation (TMS)
What is stereotaxic surgery?
Temporary pharmacological manipulations via pre-implanted micro-cannnulae to swith specific neurons/receptors on and off.
What does optogenetics involve?
Makes certain cells light-sensitive, which enables control of the activity of these individual neurons in living tissue—even within freely-moving animals—and to precisely measure the effects of those manipulations in real-time.
What brain region is thought to be important for declarative memories?
The medial temporal lobe.
What brain region is thought to be important for procedural memories?
The striatum
What brain region is thought to be important for emotional responses?
The amygdala
What did Morris et al (1982) find?
That place navigation (i.e. spatial memory) was impaired in rats with hippocampal lesions.
The hippocampus is necessary for…?
Spatial and declarative memory
What did Milner et al (1998) do?
The taxonomy of memory systems diagram - the brain systems and connections thought to be the most important for each type of memory.
In what two ways is brain connectivity studied neuroanatomically?
- Neuronal tract tracing
- Diffusion MRI
What happens in neuronal tract tracing?
PHA-L injected into a region and taken up by dendrites and cell bodies, then transported by axoplasmic flow until axons and terminal buttons can be seen under the microscope
Who is associated with diffusion MRI?
Berg-Johansen & Rushworth 2009.
What did O’Keefe et al (1998) do?
Single-unit recordings of ‘place cells’ in the hippocampus.
What sorts of electrophysiological tecnhiques are used in human studies?
- In very rare cases (e.g. pre-surgical evaluation of epilepsy patients), invasive single-unit and EEG recordings. (Engel et al, 2005)
- Surface EEG - sponataneous and evoked (event-related)
- Magnetencephalography (MEG) measures magnetic-field changes, good spatial resolution
Describe how MRI works and the two main types used.
Images are generated from an MR signal which emanates from hydrogen nuclei in brain tissue when aligned by a strong magnetic field and excited by a magnetic pulse.
Structural MRI - tissue types.
Functional MRI - brain activity based on MR changes associated with metabolic and blood flow changes. Most commonly based on the BOLD (Blood-Oxygen-Level-Dependent) MR signal.
What did Bohbot et al. (2004) do?
An fMRI study, found activation of the human hippocampus during place memory task in a virtual environment, suggesting that the hippocampus is involved in place memory.
What is a problem with Bohbot et al. (2004)’s findings?
They are correlational - just because during a place memory task the hippoocampus is activated doesn’t mean it is necessary for place memory.
What is Positron Emission Tomography (PET)?
PET is a brain activity imaging technique which involves injection of radioactive tracers that resemble compounds of interest. Dedicated detectors follow the tracers in the brain.
What did Volkow et al. (1996) do?
PET imaging of dopamine transporters, receptors and glucose metabolism in normal and Parkinson’s brains. Found evidence for dopamine defecit in Parkinson’s.
What did Krichmar et al. (2005) do?
Studied spatial learning and navigation by Darwin X, a brain-based device, improving our understanding of the function of the hippocampus in such tasks.
What are the pros and cons of MRI/PET etc?
look at ‘questions to think about’
Insert answers here!
What neurological diseases and cases can be used to imply the brain’s role in cognitive functioning?
- Stroke: blood clot
- Alzheimer’s disease
- Parkinson’s: degeneration of neurons in mid-brain - Decreases levels of dopamine: can be treated using L-dopa
- Patient Leborgne Tan’: selective speech deficit
- Phineas Gage: rod through prefrontal cortex = personality change
- Patient HM: removed part of the temporal lobe (inc. hippocampus) to treat epilepsy and although seizures stopped, he lost his episodic and semantic memory
What did Morris et al (1982) do?
- Destroyed areas of rat’s brains and put them through a spatial memory water maze task
- Rats were much slower than controls and rats with damage to areas other than the hippocampus in finding the platform they left
- Only spatial and declarative memory was impaired.
What is the hippocampus’ role in memory?
Neuronal tract tracing shows that the hippocampus gets all sorts of sensory input from many areas and integrates them - it makes sense of a structure that forms memories
What have electrophysiological techniques shown about cognitive environment maps?
Certain neurons only fire when the animal (inc. humans) is in a specific location, suggesting that they tell the animal where it is = cognitive map of environment.
What have EEGs shown about brain activity during movement in humans?
EEG showed more neuronal activity during movement (6-8x per second)
- Correlated with hippocampal memory/function
