brain imaging

Early Case Studies

• Helped localize some brain functions.

  • Damage to right side causes paralysis on opposite side → right side of body wired to left brain.

  • Damage to back of brain disrupted vision.

  • Damage to left-front part of brain produced speech difficulties.

Lesioning

• Neural cartographers can selectively lesion (destroy) tiny clusters of brain cells without impacting surrounding tissue.

  • Damage to one area of hypothalamus in rats reduces eating → starvation.

  • Damage to another hypothalamus area causes overeating.

Stimulation and Recording

• Neuroscientists can electrically, chemically, or magnetically stimulate parts of the brain.

• Use microelectrodes to detect electrical pulses in neurons → uncover individual neuron messages.

• Stimulation effects: giggling, hearing voices, turning head, out-of-body experiences.

EEG (Electroencephalogram)

• Amplifies recordings of waves of electrical activity across the brain’s surface.

• Uses electrodes covered with conductive gel placed on scalp.

• A repeated stimulus and computer filtering isolate relevant activity.

CT (Computed Tomography) Scan

• Series of X-ray photos from different angles combined into composite image.

• Shows brain’s structure and explains brain damage.

PET (Positron Emission Tomography) Scan

• Visual display of brain activity showing where radioactive tracer glucose FDG goes while brain performs psychological tasks.

• Active neurons use more glucose → colored “hot spots” appear relative to the intensity.

• Invasive

• Slow and low resolution

MRI (Magnetic Resonance Imaging)

• Uses magnetic fields and radio waves to produce 3D images or slices of soft tissue and anatomy.

• Non invasive

• High resolution

• Magnetic fields align spinning hyrdogen atoms; radio waves disorient atoms → returning spin emits signals. (maps the activity of hydrogen molecules which are present in varying degrees all over the brain)

• Findings:

  • Larger than average left-brain neural areas in musicians with perfect pitch.

  • Large ventricles (fluid) in schizophrenia patients shown with red arrows.

• MUST remove iron (including impants)

fMRI (Functional MRI)

• Reveals oxygen-laden blood flow and brain activity especially for behavioral and cognitive processes (active brain sites use more oxygen so there is more blood flow)

• Shows both brain function and structure.

• Easy to carry out

• High resolution

• Non invasive

• Film over scanning period

• Low ecological validity due to emotional responses within machine

• MUST remove iron (including impants)

Case Studies

• longitudinal - short term and long term

• holistic by looking at a range of effects of brain damage

• not repeatable ethically in a lab

• triangulation (theory, method, researcher, data)

• no manipulation/cause and effect established

• inaccurate info maybe

• combined with similar studies to form a conclusion

The Case Study of HM

• consented to experimental surgery to remove tissue from medial temporal lobe (+ hippocampus) on both sides

• had anterograde amnesia - can’t make short term into long term

• used method triangulation with IQ testing, direct observation, interviews, cognitive testing, MRI

• could not get episodic knowledge (memory for events) and semantic knowledge (general knowledge about the world) but procedural memories (motor skills) maintained

• MRI showed hippocampus had most damage —> memory not permanently stored there but plays a big role in transferring short term memories to long term ones

Hetherington and Ranson (1942)

• lesioned the ventromedial hypothalamus in rates which was believed to brake feeding

• rates increased how much they ate

• hypothalamus is linked to food control

when is it okay to experiment on an animal?

• it adds to current knowledge

• there are no alternatives

• must be applied to an ethical committee for permission

why is modern technology used?

• allows us to study brain structures and the active brain while avoiding many ethical problems with animal experimentation

• allows us to see the localization of function

Brain scanning has helped psychologists to identify brain patterns for dysfunctional behaviors. These scanning images are like fingerprints. These patterns are…

present even if the person does not show any symptoms

MRI studies

• Corkin

  • Corkin used structural MRI scans to map the exact extent of H.M.’s brain damage.

  • Earlier reports said both hippocampi were completely removed, but MRI revealed that small portions of hippocampal tissue remained, though they were nonfunctional.

  • MRI also showed damage to surrounding medial temporal lobe structures (entorhinal cortex, amygdala), helping clarify why his memory loss was so profound.

  • hippocampus is essential for forming new declarative memories.

• Maguire

  • Maguire used structural MRI to measure the size of the hippocampus in taxi drivers compared to control subjects.

  • Results: Taxi drivers had a larger posterior hippocampus and a smaller anterior hippocampus.

  • The size of the posterior hippocampus correlated with years of navigation experience.

  • This demonstrated neuroplasticity — the hippocampus can change structure in response to experience and learning.

• Case of Eugene Pauly

  • MRI revealed extensive damage to the medial temporal lobes, including the hippocampus and amygdala.

  • However, his basal ganglia and neocortex remained largely intact.

  • This imaging evidence helped explain why E.P. could not form new declarative memories but could learn habits (procedural memory).

  • MRI data supported the idea that different types of memory depend on distinct brain systems—the medial temporal lobe for declarative memory, and the basal ganglia for procedural learning.

fMRI Studies

• Baumgartner et al (2008)

  • Method (fMRI):

    • Participants played an economic trust game (investor and trustee).

    • Some received oxytocin via nasal spray; others a placebo.

    • While making trust-related decisions, participants were scanned with fMRI.

    Key fMRI Findings:

    • After betrayal, participants who received oxytocin continued to trust, while those with placebo reduced trust.

    • fMRI showed reduced activity in the amygdala (fear/emotional response) and caudate nucleus (learning from negative feedback) in the oxytocin group.

    Conclusion:

    • Oxytocin suppresses brain regions that process fear and betrayal, allowing trust to persist even after negative social experiences.

    • fMRI revealed how oxytocin modulates social emotions at the neural level.

• Harris and Fiske (2006)

  • Investigated how the brain responds to extreme social outgroups (e.g., homeless people, drug addicts) — testing the neural basis of dehumanization.

    Method (fMRI):

    • Participants viewed images of people from various social groups (e.g., rich, students, elderly, homeless).

    • While viewing, their brain activity was measured with fMRI.

    • Participants later rated emotional reactions (e.g., pity, envy, disgust).

    Key fMRI Findings:

    • Normally, when seeing people, the medial prefrontal cortex (mPFC) — involved in thinking about others’ minds — is active.

    • But for extreme outgroups (e.g., homeless or drug-addicted individuals), the mPFC showed little or no activation.

    • Instead, amygdala and insula (linked to disgust) were more active.

    Conclusion:

    • fMRI revealed that people may fail to engage social cognition networks when perceiving extreme outgroups — a neural signature of dehumanization.

• Sharot et al (2007)

  • Participants were in New York during 9/11.

  • fMRI scans occurred while they recalled memories from 9/11 and memories from the previous summer (neutral comparison).

  • Participants were grouped based on proximity to the World Trade Center during the attacks.

  Key fMRI Findings:

  • Those closer to the attacks showed greater amygdala activation when recalling 9/11 memories.

  • The strength of amygdala activation correlated with the emotional intensity and vividness of the memory.

  • For neutral memories, amygdala activation was not observed.

  Conclusion:

  • fMRI showed that emotion enhances memory vividness via amygdala-hippocampus interaction.

  • Emotional arousal strengthens memory consolidation and retrieval.