Brain Basics

Autonomic Nervous System

• The Nervous System

  • Central Nervous System (CNS)

    • The brain and spinal cord

  • Peripheral nervous system (PNS)

    • Sensory and motor neurons that connect the CNS to the rest of the body

      • Autonomic

        • Controls self-regulated action of internal organs and glands

          • Sympathetic (arousing)

          • Parasympathetic (calming)

            • Activated by yoga, deep breathes 

      • Somatic

        • Controls voluntary movements of skeletal muscles

• Neuroanatomical orientations

  • Anterior

    • near or toward front

  • Posterior

    • Near or toward back

  • Dorsal

    • Direction toward top of head or back

  • Ventral

    • Direction toward bottom of skull or front surface of body

  • Lateral

    • Toward side of body, away from middle

  • Medial

    • Toward middle, away from side

  • Coronal (or frontal section)

    • Parallel to forehead slice

  • Sagittal (or lateral section)

    • perpendicular to the ground, parallel to temporal lobes

  • Transverse (or axial section)

    • Parallel to ground

• The Forebrain

  • Human brain divided in 3:

    • Forebrain

    • Midbrain

    • Hindbrain

  • Subdivisions roughly correspond to different stages of evolutionary development

    • Neocortex

      • rational/thinking brain

    • Limbic brain

      • emotional/feeling brain

    • Reptilian brain

      • Instinctual/dinosaur brain

• Cerebral cortex

  • Part of brain best distinguishes us from other beasts

  • Outermost layer of gray matter 3mm thick

    • Outer “bark” layer

  • 26 billion neurons

  • Convulsions greatly increase surface area of brain, increasing amount of info stored

  • Mostly glia and cell bodies

    • Gives it grayish brown appearance

  • Includes neocortex

    • Phylogenetically newest part of cortex, four lobes

  • Includes limbic cortex

    • Older part of cortex

• Lobes of the brain

  • Frontal lobe

    • Speaking and muscle movements

    • Making plans and judgment

    • Emotional control

      • Primary motor cortex

        • Posterior part of frontal lobe

        • controls voluntary movements

      • prefrontal cortex

        • Anterior part of the frontal lobe

        • Formulating plans

        • Making judgment

        • Study found that size of frontal lobe directly related to size of person’s social network

        • Malleable, heavily impacted by meditation etc

  • Parietal lobe

    • Primary somatosensory cortex (anterior part of parietal lobe)

      • Surface of the body is “mapped” on the surface of the brain

        • Penfield studies

  • Occipital lobe

    • Primary visual cortex (posterior part of occipital lobe)

      • Receives visual information from opposite visual field

  • temporal lobe

    • Primary auditory cortex (superior part of temporal lobe)

      • Receives auditory information

  • Subdivisions of prefrontal cortex (emotional regulation)

    • Dorsolateral prefrontal cortex (dlPFC)

      • Working memory

      • Cognitive flexibility

      • Problem solving

        • E.g. coping with life stress

      • Inhibition of rumination and worry

    • Ventromedial prefrontal cortex (vmPFC)

      • Theory of mind (or “mindreading”)

      • Self-perception

      • Processing risk and fear

      • Behavioral control

      • Decision making

        • Includes rostral anterior cingulate cortex, medial prefrontal cortex, subgenual cingulate cortex, orbitofrontal cortex

        • Phineas Gage had damage to this area

• Lateralization of functions

  • Corpus callosum

    • Large bundle of axons, interconnects corresponding regions of association cortex on each side of brain

  • Left cerebral hemisphere:

    • Analysis of information, recognition of serial events

    • Language

    • Mathematical computation

      • Logical, linear

  • Right cerebral hemisphere:

    • Synthesis of information

    • Pattern recognition, ability to perceive things as a whole

    • identification of emotional expression

      • Non-verbal, holistic

  • Left cerebral hemisphere projects to right side of body and vice versa

  • Are people more likely to say yes to a minor request if that request is made in their right or left ear?

    • Right ear–about twice as likely

• Limbic System

  • Limbic cortex

    • Phylogenetically older part of the cortex

  • Limbic system

    • Donut shaped system of neural structures, at border of brainstem and cerebral hemispheres

    • Associated with emotions and memory

    • Includes amygdala and hippocampus

  • Amygdala

    • Two almond-shaped neural clusters

    • Linked to emotion

      • Particularly fear and aggression

    • Liberals tend to have a larger anterior cingulate cortex (assoc. w/ greater ability to cope w/ conflicting information), conservatives have larger amygdala (assoc. w/ greater ability to recognize a threat)

*****many neural structures duplicated so that one in each hemisphere, but usual convention is to refer to a structure in the singular

• Hippocampus

  • Donut-shaped structure, important in memory

  • Anterior hippocampus, portion closest to amygdala, involved in regulating behavioral inhibition in response to different contexts

    • PTSD may be linked to abnormal activity in this area

• Anterior cingulate cortex (ACC)

  • Forms “collar” around front part of corpus callosum

  • Functions:

    • Integrates cognitive and affective info

    • Awareness and processing of conflicting information

    • Selective attention

    • Pain perception

    • impulse control

• Other subcortical structures of forebrain

  • Insular cortex

    • Deep within lateral sulcus (fissure separating temporal lobe from the parietal and frontal lobes)

    • Functions:

      • Body awareness

      • Sense of self

      • Emotional experience

      • Empathy and compassion

      • Addiction

• Basal ganglia

  • Situated at base of forebrain and top of midbrain

  • Upper part (including caudate nucleus, putamen, and globus pallidus)

    • Important in action selection, motor sequencing, motor inhibition

  • Lower part (particularly nucleus accumbens)

    • Important in reward learning

• Nucleus accumbens

  • Lower part of basal ganglia

  • Reward center of brain

    • Addiction involves release of dopamine from ventral tegmental area (VTA) and substantia nigra into this area

      • Parkinson’s characterized by loss of dopaminergic neurons in this area

      • Rat will cross extremely painful electrifies grid to press level that releases dopamine in nucleus accumbens

        • Starving rat will not do this for food

• Thalamus

  • Located in center of the brain

  • Relay station for neural messages

    • Directs messages to sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla

      • Virtually all in-coming and out-going information gets routed through the thalamus

• Hypothalamus

  • Small but important neural structure lying beneath (hypo) the thalamus

  • Controls the autonomic nervous system

  • Controls the anterior and posterior pituitary glands

  • Organizes behavior related to survival, including “four f’s”

    • Fighting

    • Feeding

    • Fleeing

    • Mating

• Pituitary gland

  • Attached to base of hypothalamus

  • Controlled by hypothalamic hormones

  • Secretes hormones that control endocrine glands, including:

    • Gonadotropic hormones

      • stimulate release of sex hormones by ovaries and testes

    • Oxytocin (“cuddle hormone”)

      • Involved in social bonding and breastfeeding

    • Vasopressin

      • Regulates urine output by kidneys and plays role in pair bonding

• Areas of brain particularly important in regulation of emotions

  • Amygdala

    • Seat of emotions (fear and aggression, neg emotions)

  • prefrontal cortex PFC and anterior cingulate cortex ACC

    • Sets goals, makes plans, directs actions, shapes emotions, in part by guiding and sometimes inhibiting limbic system

  • Emotional dyscontrol often associated with overactive amygdala and underactive PFC/ACC

Midbrain

• Brain stem

  • Oldest part, central core of brain

    • Begins where spinal cord swells as it enters skull

    • responsible for automatic survival functions

• reticular formation

  • Large network of neural tissue in central part of brain stem

  • Plays part in sleep, arousal, attention, and various vital reflexes

Hindbrain

• Pons

  • Bulge in brain stem that’s part of reticular formation

    • Important in sleep and arousal, as well as sensory analysis and movement

• Medulla oblongata

  • Base of brainstem

  • Controls vital functions:

    • Heart rate

    • breathing 

    • Blood pressure

• Cerebellum

  • “Little brain” attached to rear of the bloodstream

  • Helps coordinate voluntary movement and balance

• Network neuroscience

  • Shift in recent years to studying networks or functional connectivity (how different brain regions work together) rather than just brain regions themselves

  • Traditionally, localization research almost always invokes watching how brain activity changes while a person is engaged in a particular task

  • Network research → can be done when people are doing nothing at all

    • This gets closer to person’s natural state

      • Someone with a psychological disorder will have the disorder even when not engaged in working memory task

    • Has proven to be particularly well suited to understanding schizophrenia

      • In schizophrenia, different regions of brains aren’t as densely connected

  • Important applications of network neuroscience

    • Networks not just used for diagnosis but to determine likelihood that patients will respond to different types of psychotherapy

    • If scientists can determine the circuits that a highly invasive technique like deep brain stimulation is acting upon, might be able to achieve similar results with nonsurgical approach like TMS

      • Clinicians can access regions buried in brain (like those targeted in DBS treatments for Parkinson’s) through areas closer to surface

      • It might be that best way to help a symptom that maps to a circuit is multiple electrodes or multiple stimulation sites

        • Tumor problem

• Default mode network

  • Neuroimaging and electrophysiological experiments standardly explore what happens in brain when specific tasks are being carried out

    • However, understanding what brain is doing when appears not to be doing anything is important too

  • Default mode network (DMN)

    • Brain areas that are active when participants in resting state

      • Is active when we are not focused on particular task

      • Can also be active in certain goal-oriented tasks

        • Self-referencing

        • Recognition of emotions in others

        • Remembering the past

        • Imagining the future

      • Includes posterior cingulate cortex and precuneus, medial frontal cortex, and temporoparietal junction

  • Some cognitive disorders may be correlated with impaired functioning of DMN

    • Significant correlations have been found between deteriorating connectivity of DMN over time and early indications of Alzheimer’s (rising levels of amyloid beta and tau protein)

    • May also be implicated in autism spectrum disorder, schizophrenia, bipolar disorder, depression, and PTSD

  • DMN found to be associated with ruminating about the past, worrying about future, thinking about what other people are thinking about you

    • “A Wandering Mind Is an Unhappy Mind”

    • Meditators from various traditions show reduced activity in their Default Mode Network when meditating, as well as when they are not meditating