How to study the brain

Question 1

What are the (7) main methods of psychological study?

Answer 1

• 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

Question 2

What happened to HM?

Answer 2

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.

Question 3

How are lesions experimentally induced and how else is the brain manipulated?

Answer 3

• 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)

Question 4

What is stereotaxic surgery?

Answer 4

Temporary pharmacological manipulations via pre-implanted micro-cannnulae to swith specific neurons/receptors on and off.

Question 5

What does optogenetics involve?

Answer 5

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.

Question 6

What brain region is thought to be important for declarative memories?

Answer 6

The medial temporal lobe.

Question 7

What brain region is thought to be important for procedural memories?

Answer 7

The striatum

Question 8

What brain region is thought to be important for emotional responses?

Answer 8

The amygdala

Question 9

What did Morris et al (1982) find?

Answer 9

That place navigation (i.e. spatial memory) was impaired in rats with hippocampal lesions.

Question 10

The hippocampus is necessary for…?

Answer 10

Spatial and declarative memory

Question 11

What did Milner et al (1998) do?

Answer 11

The taxonomy of memory systems diagram - the brain systems and connections thought to be the most important for each type of memory.

Question 12

In what two ways is brain connectivity studied neuroanatomically?

Answer 12

• Neuronal tract tracing
• Diffusion MRI

Question 13

What happens in neuronal tract tracing?

Answer 13

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

Question 14

Who is associated with diffusion MRI?

Answer 14

Berg-Johansen & Rushworth 2009.

Question 15

What did O’Keefe et al (1998) do?

Answer 15

Single-unit recordings of ‘place cells’ in the hippocampus.

Question 16

What sorts of electrophysiological tecnhiques are used in human studies?

Answer 16

• 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

Question 17

Describe how MRI works and the two main types used.

Answer 17

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.

Question 18

What did Bohbot et al. (2004) do?

Answer 18

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.

Question 19

What is a problem with Bohbot et al. (2004)’s findings?

Answer 19

They are correlational - just because during a place memory task the hippoocampus is activated doesn’t mean it is necessary for place memory.

Question 20

What is Positron Emission Tomography (PET)?

Answer 20

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.

Question 21

What did Volkow et al. (1996) do?

Answer 21

PET imaging of dopamine transporters, receptors and glucose metabolism in normal and Parkinson’s brains. Found evidence for dopamine defecit in Parkinson’s.

Question 22

What did Krichmar et al. (2005) do?

Answer 22

Studied spatial learning and navigation by Darwin X, a brain-based device, improving our understanding of the function of the hippocampus in such tasks.

Question 23

What are the pros and cons of MRI/PET etc?

look at ‘questions to think about’

Answer 23

Insert answers here!

Question 24

What neurological diseases and cases can be used to imply the brain’s role in cognitive functioning?

Answer 24

• 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

Question 25

What did Morris et al (1982) do?

Answer 25

• 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.

Question 26

What is the hippocampus’ role in memory?

Answer 26

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

Question 27

What have electrophysiological techniques shown about cognitive environment maps?

Answer 27

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.

Question 28

What have EEGs shown about brain activity during movement in humans?

Answer 28

EEG showed more neuronal activity during movement (6-8x per second)
- Correlated with hippocampal memory/function