Neuroscience Chapter Overview

Learning Outcomes

• This unit focuses on brain imaging technologies in investigating the relationship between biological factors and behavior.
• It also includes localization of function in the brain with examples.
• Effects of neurotransmission and functions of two hormones on behavior will be examined.
• Neuroplasticity and its effect on behavior are also discussed.

Neuropsychology

• Evolution and heritability influence actions, but aren't the sole physiological factors.
• Neuropsychology focuses on the brain and nervous system's impact on behavior.

Neurons

• Messages travel through neurons, long, thin cells of nerve tissue.
• Glia cells hold neurons in place, making up 90% of the brain.
• Neurons communicate through electrical signals called action potentials.
• Neural communication follows the all-or-none principle.

Parts of the Neuron

• Cell body: contains the nucleus and energy for the reaction.
• Dendrites: receive messages from other neurons.
• Axon: transmits messages through the neuron; often insulated with myelin containing nodes of Ranvier.
• Axon terminals: send info to other neurons.

Neurotransmission

• There's a gap, called the synaptic cleft, between axon terminals of separate neurons.
• Neurotransmitters are released from synaptic vesicles at the terminal button when the action potential reaches it.
• These neurotransmitters bind to the receptor site of the dendrite of the receiving neuron.

Action Potentials

• Unused neurotransmitters are broken down or reabsorbed by the terminal buttons through a process called reuptake.
• The message can either excite or inhibit the receiving neuron.

Synaptic Activity

• (Diagram shows the parts of the synapse: Mitochondrion, Axon, Receptor site, Synaptic vesicle, and Synaptic gap/Dendrite. Neurotransmitter is indicated.)

Neurotransmitters

• Dopamine: associated with learning, movement, emotion, and pleasure high levels cause euphoria, energy, aggression.
• Drugs overload dopamine pathways.
• Romantic love is associated with dopamine release in the ventral tegmental area (VTA).
• Serotonin: regulates mood, sleep, arousal and appetite, has an indirect effect on depression, is an inhibitory neurotransmitter, and influenced by sunlight and tryptophan-rich foods.

Agonists vs. Antagonists

• Psychoactive drugs alter brain chemistry.
• Agonists increase neurotransmitter levels.
• Antagonists decrease neurotransmitter levels.
• SSRIs (selective serotonin reuptake inhibitors) are a common example of agonists.
• Crockett et al. (2010) found SSRIs increase prosocial behavior.

Hormones

• Hormones are chemical messages sent through the endocrine system.
• Testosterone is a hormone correlated with aggression, produced in the gonads.
• Men produce considerably more testosterone than women.
• McDermott et al found a correlation between testosterone levels and aggression.
• Circadian rhythms are controlled by the suprachiasmatic nucleus (SCN) in the hypothalamus.
• Melatonin is a hormone that synchronizes the body's biological clock to the light-dark cycle, and high levels are linked to seasonal affective disorder (SAD).
• Dawn simulation is a more effective treatment for SAD than bright-light therapy (Avery et al., 2001).

Localization

• Different brain parts have specific tasks, despite some overlap.
• Strict localization claims each brain part has a specific role.
• Relative localization suggests multiple brain areas contribute to one behavior.

The Frontal Lobe

• The frontal lobe governs decision-making, planning, judgment, and emotion control.
• It's not fully mature until around age 25.
• The frontal lobe coordinates with the limbic system to control emotions.
• Harlow's study of Phineas Gage highlighted the frontal lobe's role.

Broca's Area

• Broca's Area is in the left frontal lobe, controlling speech.
• Aphasia, a language problem, includes loss of speech.
• Broca's area works with other language centers (e.g., Wernicke's area) for language comprehension.
• Broca's study of Tan demonstrated the location of the speech area.

The Hippocampus

• The hippocampus processes memories, not storing them.
• It transfers short-term memory (STM) to long-term memory (LTM).
• Different areas of the hippocampus have different roles, with the posterior part encoding spatial layouts.
• Milner and Scoville studied HM, whose hippocampus was removed.

Parts of the Brain

• (Diagram showing different parts of the brain including Cerebrum, Corpus callosum, Thalamus, Hypothalamus, Hippocampus, Brainstem, Spinal cord, Medulla, and Reticular formation (as listed in the image).

The Lobes of the Brain

• (Diagram showing the four lobes of the brain and the brain stem—the frontal, parietal, temporal, and occipital lobes—as well as the cerebellum.)

Lateralization

• The brain's two hemispheres have unique functions, with the left controlling the right and vice versa.
• The left hemisphere specializes in verbal and mathematical skills, while the right handles spatial and creative skills.
• Hemispheric differences have been oversimplified.
• Split-brain surgery removes the corpus callosum connecting the hemispheres, used to treat severe seizures(Sperry and Gazzaniga, 1968).

Neuroplasticity

• Plasticity is the brain's ability to rearrange neural connections.
• The brain can shift function to different areas after damage.
• Neural networks are systems created by plasticity, often through learning.
• Neural pruning involves removing unneeded brain connections.
• Synaptic plasticity and cortical remapping are two forms of plasticity.
• Rosenzweig and Bennett (1972) studied enriched environments and neural connections in rats.
• Draganski et al. (2004) investigated brain changes associated with juggling.

Brain Imaging

• Imaging techniques reveal brain structure and function.
• CAT scans use x-rays, PET scans radioactive substances, MRI radio frequencies and magnets, and fMRI natural blood oxygen levels.

Evaluation of Brain Scans

• Spatial resolution is the detail in the image, and temporal resolution shows how quickly changes are seen.
• Constraints exist for who can use these – CAT and PET scans and exposure to radiation, MRI and fMRI and metal use..

Research on Brain Imaging

• Harris and Fiske (2006) found reduced medial prefrontal cortex activity when people viewed extreme outgroups.
• Ashtari et al (2009) studied brain development effects in teenagers using marijuana.

Biology and Mental Disorders

• Major depression involves prolonged sadness.
• Depression has a moderate heritability (37%).
• Biological depression links are often associated with low serotonin and norepinephrine levels.
• Caspi et al. (2003) found a serotonin gene link to depression.
• Antisocial Personality Disorder (ASPD) has a relatively high heritability (41%).
• Raine et al. (1997) found less frontal lobe and amygdala activity in murderers pleading insanity.