PSYC 2650 - Chapter 2
Capgras Syndrome: An initial Example
- Capgras syndrome: rare disorder on its own, but it seems to be one of the accompaniments to Alzheimer‟s syndrome, and so is
sometimes observed among the elderly. It can also result from various injuries to the brain.
- Someone with Capgras syndrome is fully able to recognize the people in her world (husband, parents, friends) but she is utterly
convinced that these people are not who they appear to be.
- Real husband or son has been kidnapped, and the person standing before them is not the real article, but a well-trained imposter.
- In the extreme, the Capgras sufferer may murder the „imposter‟ in an attempt to end the charade and find the „genuine‟ character.
- Facial recognition involves two separate systems in the brain, one of which leads to a cognitive appraisal and the other to a more
global, somewhat emotional appraisal.
- Emotional processing is disrupted, leading to intellectual identifiable without the familiarity response. Ex. look like my father
but trigger so familiarity, so you must be someone else.
The Neural Basis for Capgras Syndrome
- Neuroimaging techniques: allow researchers to take high-quality, three-dimensional pictures of living brains, without in any
way disturbing the brains‟ owners.
- PET scans tells a great deal about the structure of the brain
- Site of damage is the temporal lobe on the right side of the head.
- This damage disrupts circuits involving the amygdala. Which seems to serve as an “emotional evaluator”
- It is also important for detecting positive stimuli
- fMRI- used to track moment-by-moment activity levels in different sites in a living brain.
- With damage in the frontal lobe, Capgras patients may be less able to keep track of what is real and what is not
What do we Learn from Capgras Syndrome
- Recognition has two separate parts (factual and emotional knowledge)
- Amygdala damage patients experience no sense of familiarity when they look at faces they know well.
- Prefrontal cortex damage patients offer crazy hypothesis about their skewed perception.
The Principle Structures of the Brain
- Human brain weights between 3 and 4 pounds
- Contains trillion nerve cells, each of which connected to 10,000 or so others, for a total for roughly 10 million billion connections
Hindbrain, Midbrain, Forebrain
- Human brain is divided into three main structures: the hindbrain, the midbrain and the forebrain
- Hindbrain: sits directly atop the spinal cord and includes several structures crucial for controlling key life functions. Ex. rhythm
of heartbeats and rhythm of breathing is controlled here. Maintain the body‟s posture and balance
- Cerebellum: largest area of the hindbrain. Coordinates our bodily movements and balance.
- Damage - problems in spatial reasoning, discriminating sounds and integrating input received from various sensory systems.
- Midbrain: coordinating our movements, including precise movements of our eyes.
- Circuits here relay auditory information from ears to areas in the forebrain where this information is processed and interpreted.
- Forebrain: largest, most interesting region.
- Cortex: outer surface of the forebrain that is visible in pictures
- It is 3mm thick, and constitutes 80% of the human brain
- Convolutions: the wrinkles on the surface of the brain made by the cortex.
- Longitudinal Fissure: deepest grove running from front of brain to back, and separating left cerebral hemisphere from right.
- Frontal Lobes: form the front of the brain, right behind the forehead
- Central Fissure: divides the frontal lobes on each side of the brain from parietal lobes, the brain‟s topmost part.
- Lateral Fissure: the bottom edge of the frontal lobes
- Temporal Lobes: below the lateral fissure.
- Occipital Lobes: at the very back of the brain, connected to the parietal and temporal lobes.
- Subcortical parts of the brain are hidden from view, underneath the cortex
- One is the thalamus: a brain region that acts as a relay station for nearly all the sensory information going to the cortex.
- Under the thalamus is the hypothalamus: a structure that plays a crucial role in the control of motivated behaviors such as eating
- Limbic system: interconnected structures that surround the thalamus and hypothalamus
- Amygdala and hippocampus, both located underneath the cortex in the temporal lobe. They are essential for learning and
memory, and for emotional processing,
- Subcortical structures come in pairs, and so there is a left hippocampus on the left side of the brain and another on the right, a
left and right amygdala too.
- There is a temporal cortex in the left hemisphere and another in the right; this also applies to the occipital cortex and so on. - Two halves of the brain work together; the functioning of one side is closely integrated with that of the other side.
- Commissures: make integration possible, these are thick bundles of fibers that carry information back and forth between
- Corpus Callosum: largest commissure
- Lesion: specific area of damage
- CT scans: use X-Rays to study the brain anatomy.
- MRI: relies on the magnetic properties of the atoms that make up the brain tissue, and it yields fabulously detailed pictures of the
- CT and MRI: relatively stable, changing only if the persons brain structure does.
- PET and fMRI: highly variable. Results depend on what task the person is performing.
Neuroimaging: An Example
- Fusiform face area (FFA): an area that seems highly responsive to faces and much less responsive to other visual stimuli
- Parahippocampal place area (PPA): brain site that seems to respond actively whenever pictures of places are in view.
- Binocular rivalry: situation when a picture of a face was out in front of one eye while a picture of a house was out in front of the
- The visual system is unable to handle both stimuli, instead the visual system seems to flip-flop between stimuli, so that for a
while the person is aware only of the face, then only of the house.
- BOLD signal (blood oxygen-aton level dependent): this measures how much oxygen the blood‟s hemoglobin is carrying in
each part of the brain, and this provides a quantitative basis for comparing activity levels in different brain areas.
Correlation vs. Causation
- Neuroimaging data tell us whether a brain area‟s activity is correlated with a particular function, but we need other data to ask
whether those brain sites play a role in causing that function.
- Transcranial magnetic stimulation (TMS): creates a series of strong magnetic pulses at a specific location on the scalp causing
a disruption in the small brain region directly underneath this scalp area.
Primary Motor Projection Areas
- Certain areas of the brain seem to be arrival points for information coming from the eyes, ears, and other sense organs, while
other areas are the departure points for signals leaving the forebrain.
- These areas are called primary projection areas with the