Introduction to biopsychology

Divisions of Biopsychology

• Direct brain manipulation is typically experimental.
• Pharmacological studies investigate how drugs affect the brain.
• Brain damage studies, known as neuropsychology, analyze the effects of lesions.
• Physiological activity measurement assesses brain function through various recordings .
• Cognitive neuroscience explores the neural basis of cognitive processes.
• Comparative studies examine brain and behavior across different species.

Central Nervous System (CNS)

• The CNS consists of the brain, skull, and spinal cord.
• Afferent nerves carry sensory information to the CNS.
• Efferent nerves transmit motor commands from the CNS to the periphery.

Peripheral Nervous System (PNS)

• The PNS is located outside the skull and spine. -The somatic nervous system controls voluntary movements. -The autonomic nervous system regulates the internal environment and homeostasis.
• The sympathetic nervous system mobilizes the body's resources, causing arousal, it is often referred to as 'fight or flight'.
• The parasympathetic nervous system conserves energy through homeostasis, a process referred to as 'rest and digest'.

Brain Support Structures

• Meninges: These membranes protect the brain, consisting of the dura mater, pia mater, and arachnoid membrane.
• Cerebrospinal Fluid (CSF): Cushions the brain within four ventricles, produced in choroid plexuses, and drains into neck veins.
• Blood-Brain Barrier (BBB): Tightly packed blood vessels that prevent certain substances from entering the brain.

Neural Cells

• Neurons: Primary cells of the nervous system responsible for communication.
• Glial Cells: Support cells: oligodendrocytes (CNS) and Schwann cells (PNS) form myelin.
• Microglia: Respond to injury and remove debris.
• Astrocytes: Control the chemical environment around neurons.

Myelination

• Glial cells create a myelin sheath around axons.
• Myelination speeds up neural conduction.

Neural Visualization Techniques

• Staining techniques show cell shapes and structures.
• Electron microscopy highlights detailed neuronal structures.
• Anterograde and retrograde tracing track neural pathways.

Brain Divisions

• Myelencephalon: Contains the medulla, involved in attention, arousal, sleep, and movement.
• Metencephalon: Includes the pons and cerebellum; crucial for cognitive functions and sensorimotor coordination.
• Mesencephalon: The midbrain, divided into the tectum and tegmentum.
• Diencephalon: Contains the thalamus and hypothalamus.
• Telencephalon: The largest division, including the cerebral cortex with sulci and gyri connecting hemispheres.

Lobes and Cortex of the Brain

• Cerebral Lobes: Frontal, parietal, temporal, and occipital.
• Neocortex: A six-layered structure with pyramidal and stellate cells.
• Hippocampus: A cortical structure with three layers.

Subcortical Structures

• Limbic System: Encircles the thalamus, involved in motivation and emotions, including the amygdala and hippocampus.
• Basal Ganglia: Involved in voluntary action and motor responses, including the amygdala, caudate, putamen, and nucleus accumbens.

Membrane Potential

• Defined as a difference in electrical charge between the inside and outside of a cell.
• Resting Potential: A neuron at rest exhibits a negative membrane potential, with the inside of the cell being more negative, in a state of polarization.

Ionic Basis of Resting Potential

• Ions are positively and negatively charged particles.
• Ion Distribution: Higher concentration of sodium outside the neuron and higher concentration of potassium inside during a resting state.
• Active Transport: Sodium-potassium pumps maintain resting potential by continuously pumping out sodium ions and pumping in potassium ions to create stability.

Postsynaptic Potentials (PSPs)

• Neurotransmitters released from presynaptic neurons bind to receptors on postsynaptic neurons, causing changes in membrane potential. -Excitatory Postsynaptic Potentials (EPSPs): Depolarizations that increase the likelihood of a neuron firing.
• Inhibitory Postsynaptic Potentials (IPSPs): Hyperpolarizations that decrease the likelihood of a neuron firing.
• Signal Strength: Determines the size of postsynaptic potentials.

Action Potentials (APs)

• Threshold: If the sum of EPSPs and IPSPs reaches -65mV, an action potential is fired.
• Depolarization: Rapid reversal of membrane potential to about +50mV.
• Sodium Channels: Voltage-activated sodium channels open, causing Na+ ions to rush into the neuron.
• Potassium Channels: Open to re-establish the resting potential.

Refractory Periods

• Absolute Refractory Period: Brief period after an AP when it's impossible to elicit another AP.
• Relative Refractory Period: Period when higher-than-normal stimulation is needed to generate another AP.
• AP Direction: Refractory periods ensure that APs travel in one direction along the axon.

Conduction of Action Potentials

• Myelination: In myelinated neurons, APs jump from one node of Ranvier to the next, speeding up conduction.

Synaptic Transmission

• Neurotransmitter Release: APs reaching terminal buttons cause the release of neurotransmitters into synapses.
• Calcium Channels: When APs arrive at the terminal buttons, calcium channels open, allowing calcium to enter, which causes synaptic vesicles to fuse with the presynaptic membrane and release their contents into the synapse.
• Signal Termination: Synaptic messages are terminated through reuptake or enzymatic degradation.

Neurotransmitters

• Categories: Neuropeptides and small molecule transmitters.
• Amino Acids: Glutamate (excitatory) and GABA (inhibitory) are the most prevalent.
• Monoamines: Dopamine, epinephrine, norepinephrine, and serotonin.

Drug Effects on Synaptic Transmission

• Agonists: Drugs that facilitate neurotransmitter effects.
• Antagonists: Drugs that inhibit neurotransmitter effects.

Psychophysiological Measures

• Electromyography (EMG): Measures muscle tension through electrodes on the skin.
• Electrooculography (EOG): Measures eye movements through electrical potential between the front and back of the eyeball, linked to the somatic nervous system.
• Skin Conductance: Emotions increase skin conductance, measured as Skin Conductance Level (SCL) for background level and Skin Conductance Response (SCR) for transient changes.
• Cardiovascular Activity: Emotions affect heart rate, blood pressure, and blood volume, controlled by the Autonomic Nervous System (ANS).

Electrophysiological Measures

• Intracellular (IC) Recording: Measures fluctuations in a neuron's membrane potential.
• Extracellular (EC) Recording: Measures action potentials.
• Electroencephalography (EEG): Measures electrical activity through electrodes on the scalp. Includes action potentials, PSPs, etc., and shows different waveforms showing states of consciousness.
• Event-Related Potential (ERP): EEG waves associated with specific psychological events, composed of signal and background noise, and uses signal averaging to amplify the signal and cancel out background noise.
• Magnetoencephalography (MEG): Measures magnetic fields related to electrical activity using Superconducting Quantum Interference Devices (SQUIDs), requires cooling, and has better spatial resolution than EEG.

Brain Imaging Techniques

• Structural Imaging: Uses physical properties of brain tissue to create images.
• Cerebral Angiography: Involves injecting a contrast agent into the bloodstream during an X-ray.

Brain Imaging: Computed Tomography (CT)

• CT scans use X-ray absorption.
• Bone absorbs the most X-rays, while CSF absorbs the least.
• CT scans cannot measure functional brain activity.

Brain Imaging: Magnetic Resonance Imaging (MRI)

• MRI provides high-resolution structural images.
• It uses radiofrequency waves and does not involve radiation.
• MRI can distinguish between white and gray matter.

Brain Imaging: Functional MRI (fMRI)

• fMRI shows brain activity.
• It measures Blood-Oxygen-Level-Dependent (BOLD) signals.
• The spatial resolution of fMRI is approximately 1mm.

Brain Imaging: Diffusion Tensor Imaging (DTI)

• DTI visualizes pathways of water diffusion in the brain.

Brain Imaging: Positron Emission Tomography (PET)

• PET involves injecting radioactive tracers into the bloodstream, which emit positrons that are detected.
• PET has largely been replaced by fMRI but is still useful for mapping pathways.

Brain Stimulation Techniques

• Transcranial Magnetic Stimulation (TMS): Uses a magnetic field to stimulate neurons.
• TMS is non-invasive but can disrupt cognitive processes.
• Transcranial Direct Current Stimulation (tDCS) and Transcranial Alternating Current Stimulation (tACS): Stimulate the brain via electrodes on the scalp.
• tDCS involves applying a weak current between an anode and a cathode.

Applications of Brain Stimulation

• Useful in sleep research.
• Allows for Brain-Computer Interfaces (BCI).
• Useful as Neurofeedback.

The Visual System

• The visual system is based on the perception of light waves, or electromagnetic energy.
• Wavelength determines color.
• Retina: Contains five neuron types arranged inside-out.
• Fovea: A central pit in the retina causing distortion.
• Optic Nerve: Creates a blind spot compensated for by completion.
• Cones: Specialized for good lighting, color perception, and central vision.
• Rods: Function in dim illumination, providing less detail and color and are used for peripheral vision.

The Auditory System

• Pathway: Cochlea to auditory cortex.
• Medial Superior Olives: Respond to differences in arrival time between ears.
• Lateral Superior Olives: Detect differences in amplitude.

The Somatosensory System

• The exteroceptive system perceives external stimuli through receptors on the skin.
• Proprioceptive system perceives body position in space.
• Interoceptive system perceives bodily conditions.

Chemical Senses

• Olfaction (smell) and gustation (taste) monitor chemical content in the environment, combined to create flavor.
• Olfactory Pathway: Travels through the olfactory bulb to the cortexes.
• Gustatory Pathway: Travels from taste buds to the insula.

Stages of Visual Perception

• Edges and Contrast: Crucial for initial perception.
• Lateral Inhibition: When a receptor fires, it inhibits its neighbors.
• Receptive fields in fovea are smaller, allowing for higher detail.
• Depth Perception: Achieved through binocular disparity.
• Object Recognition:
  • Edges and contrast are initially identified.
  • Higher-order units (figures) are recognized.
  • Matching with stored representations occurs.
  • Meaning is attributed to the object.

Process of Perception

• Perception: Apprehending objects and events in the environment.
• Outcome: A percept.
• Stages: Involves sensation, perceptual organization, and identification. -Sensory Adaptation: More responsive to change than to steady states
• Adaptation: Diminishing responsiveness of sensory systems to prolonged output.

Focus of Attention

• Attention allows us to direct our awareness to specific information, enabling us to perceive and learn about it.
• Selectivity: The attentional system acts as a filter due to limitations in processing capacity.
• Attentional Selection: Can be directed towards regions of space, features, objects, and time windows.
• Modulators: Influenced by salience (bottom-up), goals and expectations (top-down), and memory (priming).
• Neural Network: The parietal lobes and the frontal eye fields are part of the attention network.

Visual Perception Disorders

• Visual Agnosia: Disorders of object recognition.
• Scotoma: Damage to V1 leading to a blind area in the visual field.
• Blindsight: Ability to unconsciously respond to stimuli in a scotoma.
• Prosopagnosia: Failure to recognize faces.
• Autism: Specific increases and decreases in sensitivity to stimuli.

Causes of Brain Damage

• Brain Tumors: Can be benign or malignant.
• Gliomas: Tumors from glial cells are common and rapidly growing.
• Metastatic Tumors: Originate elsewhere in the body and spread to the brain.
• Strokes: Cerebral hemorrhage (bleeding due to ruptured blood vessels, caused by an aneurysm).
• Cerebral Ischemia: Lack of blood flow due to thrombosis.
• Role of Glutamate: Blood-deprived neurons become over-reactive and release excessive glutamate, causing excitotoxicity.
• Brain Injuries: Closed head injuries can cause contusions and mild Traumatic Brain Injury (TBI).
• Infections of the Brain: Bacterial infections lead to abscesses and meningitis.
• Syphilis: Can lead to dementia.
• Neurotoxins: Toxic chemicals from external or internal sources, such as heavy metals or cortisol.
• Genetics: Neuropsychological diseases caused by abnormal recessive genes and genetic accidents.

Neurological Diseases

• Epilepsy: Seizures generated by chronic brain dysfunction.
• Focal Seizures: Affect a specific brain area.
• Generalized Seizures: Affect the entire brain.
• Types of Seizures: Tonic-clonic and absence seizures.
• Parkinson's Disease: Movement disorder characterized by tremor and slowness; degeneration of neurons in the substantia nigra.
• Multiple Sclerosis (MS): Autoimmune disease attacking myelin sheaths in the CNS, leading to visual disturbances and weaknesses.
• Alzheimer's Disease: Characterized by neurofibrillary tangles, amyloid plaques, and neuron loss in the amygdala and hippocampus.
  • Progression: Preclinical, prodromal, and dementia stages.

Responses to Nervous System Damage

• Neural Degeneration: Neural deterioration and death, including anterograde degeneration (of the distal segment) and retrograde degeneration (of the proximal segment).
• Neural Regeneration: Regrowth of damaged neurons, primarily occurs in the PNS.
• Neural Reorganization: The brain can rewire itself, with undamaged areas taking over functions from damaged areas.
• Recovery of Function: More likely after small lesions and in younger patients.
  • Cognitive Reserve: The brain’s ability to use alternative strategies to accomplish tasks.

Defining Sleep

Sleep is a periodic state of rest for the mind and body with complete or partial loss of consciousness.

Measuring Sleep

• Polysomnography (PSG): Measures sleep using several techniques.
  • Electroencephalography (EEG): Measures brain electrical activity.
  • Electrooculography (EOG): Measures eye movements.
  • Electromyography (EMG): Measures muscle activity.
• PSG helps measure different stages of sleep.

Stages of Sleep

• Awake: Low amplitude, irregular, high frequency brain waves.
• Drowsy: Alpha waves.
• Stage 1 Sleep: Theta waves.
• Stage 2 Sleep: Sleep spindles and K complexes.
• Stage 3 Sleep: Delta waves.
• REM (Rapid Eye Movement) Sleep: Low voltage, random fast activity, rapid eye movement.

Why We Sleep Theories

• Regenerative Theories: Sleep restores physiological balance (homeostasis) and keeps internal biochemical systems balanced.
• Circadian and Adaptive Theories: Sleep conserves energy and protects us during darkness.

Sleep Deprivation Effects

• Causes alterations in cognition, mood, and physiological functions.
• It is often difficult to isolate sleep loss from stress factors.
• Sleep deprivation results in increased sleepiness, negative emotions and impaired attention.
• Extended sleep deprivation leads to microsleeps and REM rebound.
• Can be fatal due to accumulation of the above effects..

Understanding Circadian Rhythms

• Biological cycles that last around 24 hours.
• Regulated by Zeitgebers, particularly light.
• The Suprachiasmatic Nucleus (SCN) in the hypothalamus is the primary regulator of these cycles.

Biology Behind Sleep

• Hypothalamus: Links the nervous and endocrine systems.
• SCN: Key structure for circadian rhythm regulation.

How Sleep Benefits Learning and Memory

• Two-Stage Model of Memory: Involves initial storage in the hippocampus and transfer to the cortex.
• Dual-Process Theory: Different types of sleep are responsible for consolidating different types of memories (SWS and REM).
• Sequential Hypothesis: Learning requires a sequence of sleep stages with a weakening of non-adaptive memories in SWS and storage of adaptive memories in REM.
• Active System Consolidation Hypothesis: Spatio-temporal activity patterns are reactivated during SWS; memory improvements require intact sleep cycles, and sleep can strengthen individual memories via reactivation during sleep.

Theory About Dreaming

• Dreaming: Strongly associated with REM sleep.
• Dreams: External stimuli can be incorporated into dreams, which tend to run in "real time".
• Activation-Synthesis Hypothesis: Dreams result from the cortex trying to make sense of random information it receives during REM sleep.
• Lucid Dreaming: Occurs when one becomes aware that they are in a dream.