PSYC10003 · Mind, Brain and Behaviour 1
Brain Imaging, Plasticity and Integration
Week 8 surveys the methods used to image and modify the brain — structural versus functional imaging (MRI vs fMRI, EEG, PET) and stimulation techniques (TMS, tDCS, ECT) — and what each can and cannot reveal, trading off spatial against temporal resolution and correlation against causation. It then covers neuroplasticity (long-term potentiation and depression, neurogenesis) and how distributed regions integrate to produce behaviour and emotion. The examinable skill, within the 25% Behavioural Neuroscience block, is matching each method to the question it answers and explaining plasticity with concrete mechanisms.
What this chapter covers
- 01Structural imaging (MRI, DTI) vs functional imaging (fMRI, EEG, PET); what each measures
- 02Spatial vs temporal resolution trade-off; EEG (great temporal, poor spatial) vs MRI/fMRI (great spatial)
- 03fMRI measures the BOLD signal with a haemodynamic delay; provides correlational information
- 04PET uses radioactive tracers to image metabolism and specific neurochemistry
- 05Stimulation gives causal information: TMS as a temporary 'virtual lesion'; tDCS; ECT for severe depression
- 06Synaptic plasticity: long-term potentiation (LTP, 'fire together, wire together') and long-term depression (LTD)
- 07Neurogenesis, largely restricted to the hippocampus and olfactory bulb; rehabilitation after injury
- 08Functional connectivity and integration; the amygdala coordinating the emotional response
Matching the method to the research question
- +1(i) Precise millisecond timing calls for EEG, which has excellent temporal resolution (its weakness is poor spatial resolution / localising deep sources).
- +1(ii) A high-resolution structural image calls for structural MRI, which gives very high spatial resolution of anatomy (its cost and magnet-safety constraints are the trade-off).
- +1(iii) Testing whether a region is causally necessary calls for a stimulation method — transcranial magnetic stimulation (TMS), a temporary 'virtual lesion' that briefly disrupts the region; unlike imaging, stimulation yields causal information.
- +1(iv) Imaging specific neurochemistry (dopamine receptors) calls for PET, which uses radioactive tracers to visualise metabolism and neurotransmitter/receptor function. (v) fMRI tracks the BOLD signal with a haemodynamic delay and only correlates activity with behaviour, so its evidence is correlational, not causal.
Key terms
- Structural vs functional imaging
- Structural imaging (e.g. MRI) shows anatomy; functional imaging (e.g. fMRI, EEG, PET) shows activity. Structural answers 'what does it look like', functional answers 'what is it doing'.
- Spatial vs temporal resolution
- The precision with which a method localises activity in space versus in time. EEG has excellent temporal but poor spatial resolution; MRI/fMRI have excellent spatial resolution but fMRI is limited in time by the haemodynamic delay.
- BOLD signal
- The blood-oxygen-level-dependent signal that fMRI measures — active regions draw more oxygenated blood, changing the magnetic signal, with a delay of a few seconds; it is correlational.
- Transcranial magnetic stimulation (TMS)
- A focal magnetic pulse that briefly disrupts a small cortical region — a temporary 'virtual lesion' — giving causal evidence about whether a region is necessary for a task.
- Long-term potentiation (LTP)
- The lasting strengthening of a synapse when its activation is repeatedly paired with postsynaptic firing — 'neurons that fire together, wire together' — a cellular basis of learning; its opposite is long-term depression (LTD).
- Neurogenesis
- The generation of new neurons, in adults largely restricted to the hippocampus and olfactory bulb; because most destroyed neurons are not replaced, recovery after injury relies mainly on LTP/LTD-based rewiring of surviving neurons.
Brain Imaging, Plasticity and Integration FAQ
Why can't fMRI show causation?
Because fMRI measures the BOLD signal — a blood-flow proxy for activity with a few-seconds delay — and only shows that a region's activity correlates with a task. To show a region is necessary you need to intervene, for example with TMS (a temporary virtual lesion) or a lesion study; those give causal information.
What is the trade-off between EEG and fMRI?
EEG has superb temporal resolution (millisecond timing) but poor spatial resolution and mostly sees cortical-surface activity; fMRI has excellent spatial resolution but poor temporal resolution because of the haemodynamic delay. The choice depends on whether the question is about when or where.
What is the difference between LTP and LTD?
Long-term potentiation strengthens frequently co-activated synapses ('fire together, wire together'), making the postsynaptic neuron more responsive; long-term depression weakens rarely used synapses ('use it or lose it'). Together they let the brain adapt its connectivity to experience — the cellular basis of learning and of rehabilitation after injury.
Does the adult brain grow new neurons?
Only to a limited extent — adult neurogenesis is largely restricted to the hippocampus (memory) and the olfactory bulb (smell). Most destroyed neurons are not replaced, so recovery after stroke or trauma depends mainly on surviving neurons rewiring through LTP and LTD, not on new cells.
How is this examined?
As method-matching MCQs (which technique answers which question, and its resolution/invasiveness/cost trade-offs) and as conceptual plasticity items (what LTP/LTD do, where neurogenesis occurs). You are not asked to interpret raw scans, but you must know what each method can and cannot reveal.
Exam move
Build a comparison table of the imaging and stimulation methods with columns for what they measure, spatial resolution, temporal resolution, and correlational-vs-causal, then rehearse picking the right tool for a stated aim. Keep one crisp line for each: EEG = timing, MRI = structure, fMRI = correlational BOLD, PET = chemistry, TMS = causal virtual lesion. For plasticity, pair LTP ('fire together, wire together') with LTD ('use it or lose it') and remember neurogenesis is largely hippocampus and olfactory bulb. This is a conceptual block, so drill the distinctions rather than memorising numbers. Confirm exam details on Canvas.
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