The Biology of Behavior and Consciousness

Chapter 2: The Biology of Behavior and Consciousness

Brain Regions and Brain Structures (Part 1)

  • Main divisions of the human brain:

    • Hindbrain:

    • Directs essential survival functions such as:

      • Breathing

      • Sleeping

      • Wakefulness

      • Coordination

      • Balance

    • Midbrain:

    • Controls some motor movements.

    • Transmits auditory and visual information.

    • Forebrain:

    • Manages complex cognitive activities, sensory and associative functions, and voluntary motor activities.

Brain Regions and Brain Structures (Part 2)

  • Brainstem:

    • Central core of the brain, beginning where the spinal cord swells as it enters the skull.

    • Responsible for automatic survival functions.

  • Medulla:

    • Hindbrain structure at the base of the brainstem.

    • Controls heartbeat and breathing.

  • Pons:

    • Aids in coordinating movement and controlling sleep.

Brain Regions and Brain Structures (Part 3)

  • Thalamus:

    • The brain's sensory control center, located at the top of the brainstem.

    • Directs sensory messages to the cortex and transmits replies to cerebellum and medulla.

  • Reticular formation:

    • Nerve network running through the brainstem and thalamus.

    • Acts as a filter relaying important information to other brain areas.

    • Plays an important role in controlling arousal.

Brain Regions and Brain Structures (Part 4)

  • Cerebellum:

    • Known as the "little brain"; situated at the rear of the brainstem.

    • Aids in:

    • Judgment of time.

    • Discrimination of sound and texture.

    • Emotional control.

    • Coordination of voluntary movement.

    • Life-sustaining functions.

    • Processing and storing memories of things that cannot be consciously recalled.

Brain Regions and Brain Structures (Part 6)

  • Limbic system:

    • A neural system located between the oldest and newest brain areas.

    • Associated with emotions and drives.

    • Components include:

    • Amygdala:

      • Two almond-shaped neural clusters; enable aggression and fear; linked to emotion.

    • Hypothalamus:

      • Positioned below the thalamus; linked to emotion and reward.

      • Directs several maintenance activities and helps govern the endocrine system via the pituitary gland.

    • Hippocampus:

      • Plays a role in processing conscious, explicit memories of facts and events.

Brain Structures and Their Functions (Part 8)

  • Amygdala:

    • Linked to emotion (located in both hemispheres).

  • Hippocampus:

    • Linked to conscious memory (located in both hemispheres).

  • Cerebral Cortex:

    • Ultimate control and information-processing center.

  • Corpus Callosum:

    • Composed of axon fibers connecting the two cerebral hemispheres.

  • Thalamus:

    • Relays messages between lower brain centers and the cerebral cortex.

  • Hypothalamus:

    • Controls maintenance functions such as eating and governs endocrine system; linked to emotion and reward.

  • Pituitary Gland:

    • Master endocrine gland.

  • Reticular Formation:

    • Helps control arousal.

  • Pons:

    • Aids in coordinating movement and controlling sleep.

  • Medulla:

    • Controls heartbeat and breathing.

  • Spinal Cord:

    • Pathway for neural fibers traveling to and from the brain; controls simple reflexes.

  • Cerebellum:

    • Coordinates voluntary movement and balance, supports skill learning and memory.

Cerebral Cortex

  • Definition:

    • The brain’s "thinking crown," characterized by its wrinkled outer surface.

    • Makes up approximately 80% of the brain's total mass.

  • Functions:

    • Handles higher-level functions including:

    • Perception

    • Language

    • Memory

    • Decision-making

    • Voluntary movement.

    • Essentially what makes humans distinctively "human."

  • Structure:

    • Divided into two hemispheres (left & right).

    • Each hemisphere contains four lobes:

    • Frontal

    • Parietal

    • Temporal

    • Occipital.

Functions of the Cerebral Cortex (Part 1)

  • Motor Functions:

    • Achieved through electrical stimulation of specific cortex parts to enable body movements.

    • The motor cortex is the cerebral cortex area at the rear of the frontal lobes that controls voluntary movements.

  • Sensory Functions:

    • The somatosensory cortex is the cerebral cortex area at the front of the parietal lobes, responsible for registering and processing sensations related to body touch and movement.

    • The sensitivity of body regions relates directly to the size of the somatosensory area dedicated to it.

Functions of the Cerebral Cortex (Part 4)

  • Visual Cortex:

    • Located in the occipital lobes at the rear of the brain; receives input from the eyes.

  • Auditory Cortex:

    • Located above the ears in the temporal lobes; receives auditory information from the ears.

The Cerebral Cortex (Part 5)

  • Psychoactive Drug LSD:

    • Often produces vivid hallucinations due to dramatically increased communication between the visual cortex (in the occipital lobe) and other brain regions.

The Cerebral Cortex (Part 6)

  • Association Areas:

    • Involved in higher mental functions such as:

    • Learning

    • Thinking

    • Remembering

    • Speaking.

    • Found in all four lobes of the cerebral cortex.

    • The prefrontal cortex in the frontal lobe enables functions like:

    • Forward thinking

    • Judgment

    • Planning

    • Processing of new memories.

    • Damage in this area can result in inhibited planning, personality changes, reduced intelligence test scores, and other cognitive impairments, varying with the lobe affected.

The Cerebral Cortex (Part 8)

  • Phineas Gage:

    • His skull serves as a medical record highlighting significant personality changes post-accident:

    • Became more impulsive.

    • Exhibited rude behavior.

The Divided Brain (Part 1)

  • Corpus Callosum:

    • A large band of neural fibers connecting both brain hemispheres, facilitating communication between them.

The Divided Brain (Part 3)

  • In an intact brain:

    • Data received by one hemisphere quickly transmits to the counterpart.

  • In a brain with a severed corpus callosum:

    • This information sharing is disrupted.

The Divided Brain (Part 5)

  • Right–Left Differences in Intact Brains:

    • Human brains are unified systems with specialized areas.

  • Each hemisphere of the brain performs distinct functions:

    • Left Hemisphere:

    • Proficient at rapidly and accurately interpreting language.

    • Right Hemisphere:

    • Excels at making inferences and reasoned conclusions.

    • Assists in refining human speech.

Brain States and Consciousness (Part 2)

  • Consciousness:

    • Defined as subjective awareness of the self and the environment.

    • Enables voluntary control and the communication of mental states to others.

    • Aids in focusing attention.

  • Conscious Awareness:

    • Not localized in any particular small brain area but a product of coordinated cortex-wide activity.

Brain States and Consciousness (Part 4)

  • Conscious focus on new tasks can involve:

    • Sequential Processing:

    • Processing of multiple tasks in a sequence.

    • Parallel Processing:

    • Simultaneous processing of multiple tasks.

    • Altered states of consciousness:

    • Variants from typical waking consciousness, including various effects of external substances or influences.

Selective Attention: Inattentional Blindness

  • Selective Attention:

    • Described as a conscious focus that resembles a flashlight beam concentrating on a very small segment of all experiences.

  • Inattentional Blindness:

    • Indicates instances where individuals focusing on basketball tosses amongst black-shirted players often fail to notice an umbrella-wielding woman crossing the screen.

Selective Attention (Part 1)

  • Driving simulation experiments show:

    • Individuals whose attention was diverted by text messages or cell phone conversations made more driving errors.

    • In studies regarding teenage drivers, distractions from passengers or phones contributed to 58% of crashes.

Sleep and Dreams (Part 1)

  • Sleep:

    • Defined as a periodic, natural loss of consciousness distinct from unconsciousness due to coma, general anesthesia, or hibernation.

    • The human auditory cortex continues to respond to sound stimuli during sleep.

  • Biological Rhythms:

    • 24-hour Biological Clock:

    • Known as the circadian rhythm, indicating regular bodily rhythms operating on a 24-hour cycle.

    • Altered by factors such as age and experience.

Sleep and Dreams (Part 4)

  • EEG Activity During Sleep:

    • When awake yet relaxed, EEG detects alpha waves.

    • As fatigue develops, progresses into sleep stages:

    • N1 → N2 → N3 → back to N2 → REM.

  • Stages of Sleep:

    • N1 Sleep:

    • Characterized by irregular brain waves from the non-REM sleep stage (alpha waves) with potential hypnagogic sensations (e.g., falling).

    • N2 Sleep:

    • Deeply relaxed state lasting around 20 minutes with EEG showing bursts of rapid, rhythmic brain-wave activity.

    • N3 Sleep:

    • Deep sleep stage lasting approximately 30 minutes, characterized by delta waves.

Sleep and Dreams (Part 2)

  • REM Sleep:

    • Known as rapid eye movement sleep; it is a recurring sleep stage during which vivid dreams commonly occur.

    • Often referred to as paradoxical sleep, during which muscles are relaxed (except for minor twitches), but other bodily systems remain active.

REM Sleep (Part 2)

  • During REM sleep:

    • Both male and female genitalia are aroused, regardless of dream content.

    • The brain’s motor cortex is active, while the brainstem inhibits its messages, resulting in muscle relaxation.

    • This paradoxical sleep demonstrates internal arousal with external calmness.

    • The sleep cycle repeats approximately every 90 minutes, with increasing REM and N2 periods.

The Stages in a Night's Sleep

  • Stages of Sleep Progression (in Hours):

    • For Young Adults:

    • The progression enhances REM sleep as the night continues.

    • Structure over sleep hours:

      • Awake → REM → N1 → N2 → N3 → Awake → REM → N1.

    • For Older Adults:

    • Sleep stages vary with some reports indicating shorter cycles with less REM.

Why Do We Sleep? (Part 2)

  • Functions of Sleep:

    • Protects the organism.

    • Aids in recovery processes.

    • Restores and organizes memories of daily experiences.

    • Encourages creative thinking.

    • Supports growth and physical health.

Sleep Deprivation and Sleep Disorders (Part 1)

  • Effects of Sleep Loss:

    • Impacts mood and increases the risk of depression.

    • Leads to reduced resistance to viral infections and cancers.

    • Decreases reaction time and raises error incidents; refers to microsleep and decreased driving safety.

    • Impairs academic performance and can promote weight gain by influencing hormones:

    • Increases levels of ghrelin (hunger hormone);

    • Decreases levels of leptin (satiety hormone);

    • Increases cortisol production (stress hormone);

    • Amplifies limbic brain responses leading to food-related cravings.

Sleep Deprivation and Sleep Disorders (Part 3)

  • Recommended Practices for Better Sleep:

    • Engage in regular exercise, avoiding late evenings.

    • Refrain from caffeine after early afternoon and limit food/drink intake before bed (milk as an exception).

    • Create a calm environment by dimming lights before bed.

    • Maintain a fixed schedule for waking times, even after restless nights.

    • Avoid checking time displays to reduce anxiety.

    • Acknowledge that temporary sleep loss is usually not harmful.

    • Channel thoughts to calm, engaging topics (e.g., song lyrics or vacation plans) rather than fixating on falling asleep.

    • Manage stress levels to improve sleep quality.

Sleep Deprivation and Sleep Disorders (Part 4)

  • Major Sleep Disorders:

    • Insomnia:

    • Refers to difficulty falling asleep or staying asleep.

    • Narcolepsy:

    • Characterized by sudden sleep episodes occurring randomly, sometimes immediately into REM sleep.

    • Sleep Apnea:

    • Breathing appears to pause repeatedly during sleep, causing brief awakenings.

    • Night Terrors:

    • Episodes of intense fear during sleep common in children; different from nightmares because the individual isn’t fully awake and doesn’t usually remember them.

Dreams

  • Definition of Dreams:

    • Sequences of images, emotions, and thoughts that pass through a sleeping person's mind during sleep.

  • REM Dreams:

    • Are typically vivid, emotional, and often bizarre. Common themes involve negativity such as:

    • Falling

    • Being attacked or pursued

    • Experiencing misfortune.

  • The brain monitors the environment continually during sleep, incorporating sensory stimuli into dream content.

Why Do We Dream?

  • The reasons for dreaming include:

    • To fulfill personal wishes, according to Freud (manifest content and latent content).

    • To file away and organize memories (information-processing theory).

    • To develop and sustain neural pathways.

    • To interpret neural static (brain activity).

    • To reflect cognitive development associated with brain maturation.