Neurons: The primary nerve cells in the brain, consisting of dendrites (receive
stimulation) and axons (transmit messages).
A erent Nerves: Long dendrites extending from the central nervous system to
the body, transmitting sensory information to the brain.
E erent Nerves: Long axons sending impulses from the central nervous system
to muscles, glands, and organs.
Interneurons: Short axons or none, regulate transmissions between nerve cells,
with the largest bundle forming the brain.
Brain Anatomy
Thalamus:
Regulates arousal and other functions.
Hypothalamus:
Located beneath the thalamus, near the bottom center of the brain, above the
roof of the mouth.
Connected to almost everything else in the brain, its nerves extend throughout,
and it secretes hormones a ecting the entire body.
Amygdala:
Situated behind and to the sides of the hypothalamus.
Plays a crucial role in emotion.
Hippocampus:
Located near the amygdala.
Essential for processing memories.
Cortex (Cerebral Cortex):
Outer layer of the brain, wrapped around inner organs.
Composed of six layers with di erent anatomical and functional properties.
The outermost layer, the neocortex, is particularly complex and wrinkled in
humans.
Frontal Cortex
Structure:
, Divided into two lobes (right and left) at the front of the brain.
Functions:
Cognitive Abilities:
Planning ahead and anticipating consequences.
Emotional Experience:
Empathy and moral reasoning.
Summary
The brain and its extensive network of nerves form the physical basis of personality.
Neurons transmit sensory information to the brain, connect these sensations with
feelings and memories, and send behavioral instructions to the muscles.
Key brain regions such as the hypothalamus, amygdala, hippocampus, and various
layers of the cortex play vital roles in regulating emotions, processing memories, and
supporting cognitive functions unique to humans
Research Methods for Studying the Brain
Brain Damage
Historical Observations:
Knowledge about the brain has historically come from observing people with
head injuries.
Specific problems caused by damage to di erent parts of the brain provide
insights into brain function.
Deliberate Brain Surgery:
Researchers sometimes perform brain surgeries on animals, such as rats and
monkeys, by lesioning (destroying) or removing parts of the brain.
The study of animal personality reveals traits such as reactivity, dominance,
openness, extraversion, and agreeableness in various species, including
chimpanzees, macaques, and even squid (Freeman et al., 2013; Adams et al.,
2015; Sinn et al., 2008).
Brain Stimulation
Electrodes and Stimulation:
Stimulating the brain with electrodes can produce di erent experiences, such as
visions, sounds, and memory flashbacks (Penfield & Perot, 1963).
Example: Stimulation of the left substantia nigra caused severe depression in a
Parkinson’s patient, which vanished when stimulation was stopped (Bejjani et
al., 1999).
, Transcranial Magnetic Stimulation (TMS):
Uses magnetic fields to temporarily "knock out" brain areas, creating virtual
lesions without physical cutting (Fitzgerald et al., 2006).
Example: Temporarily disabling speech areas results in the inability to talk
(Highfield, 2008).
Transcranial Direct Current Stimulation (tDCS):
Shows the right frontal lobe's role in making morally relevant decisions (Knoch et
al., 2008).
Brain Activity and Imaging
Electroencephalography (EEG):
Electrodes on the scalp detect electrical signals from brain activity.
Useful for determining when the brain is active, but not where the activity is
located.
Magnetoencephalography (MEG):
Detects magnetic indications of brain activity with delicate sensors.
Computed Tomography (CT) Scans:
Combine X-ray images to create detailed slices of the brain.
Positron Emission Tomography (PET) Scans:
Map brain activity by following a radioactive tracer in the bloodstream.
Functional Magnetic Resonance Imaging (fMRI):
Monitors magnetic pulses generated by oxygen in the blood to map brain activity.
Measures blood oxygen level-dependent (BOLD) signals to identify active brain
regions.
Di usion Tensor Imaging (DTI) and Magnetic Resonance Spectroscopy (MRS):
Newer methods providing more detailed brain imaging.
Challenges and Considerations
Metabolic Activity:
All parts of the brain are always active to some degree, making it challenging to
measure specific activities.
Techniques like perfusion imaging o er more precise measures but rely on
similar logic to BOLD signals.
Correlation vs. Causality:
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