diencephalon, basal ganglia and nucleus accumbens

where is the diencephalon located

top of the brainstem but below cerebral cortex

what are the 4 main regions of diencephalon

• thalamus

• subthalamus

• hypothalamus

• epithalamus

what is thalamus (structure and function)

2 large symmetrical lobes

acts as the brain's primary sensory relay station, directing nearly all sensory information (except smell) to the cerebral cortex for processing, while also crucially regulating consciousness, sleep, alertness, motor control, and integrating sensory and cognitive function

main function of thalamus

to relay and process sensory information (except smell) before sending it to the cerebral cortex

how does thalamus interact with sensory system

each sensory system (except olfactory) has a thalamic nucleus that receives signals and sends them to the corresponding cortical area

why is thalamus called ‘relay station’

because it receives, processes and forwards info between lower brain regions and cortex

what role does the thalamus play in sleep and consciousness

helps to regulate sleep and wakefulness through thalamo-cortico-thalamic circuits linked to consciousness

what forms the thalamo-cortico-thalamic circuits

thalamic nuclei have strong reciprocal connections with cerebral cortex

what happens if thalamus is damaged

can cause:

• coma

• amnesia

• impaired sensation

• movement

• pain

• dementia

• sleepiness

which cognitive disorders are associated with thalamic dysfunction

• bipolar disorder

• ADHD

• autism

• depression

• Alzheimer’s disease

what is hypothalamus and where is it located

small region below the thalamus that controls many unconscious bodily functions

main function of hypothalamus

to maintain homeostasis — stable internal conditions such as temperature, hunger, thirst, and sleep

how does hypothalamus control hormones

regulates pituitary gland which controls most of hormones

key functions regulated by hypothalamus

• body temp

• hunger

• thirst

• fatigue

• sleep

what happens when hypothalamus is damaged

can cause aggression, hypothermia, hypersomnia, weight changes, chronic stress, and lethargy

which disorders are linked to hypothalamic dysfunction

• depression

• bipolar disorder

• schizoprenia

what is the epithalamus

dorsal posterior part of the diencephalon that includes several small nuclei and the pineal gland

main function of epithalamus

to secrete melatonin via the pineal gland, regulating the circadian rhythm (sleep–wake cycle)

what brain systems is the epithalamus connected to

limbic system (emotion) and basal ganglia (movement)

what happens if the pineal gland is damaged

disruption of circadian rhythms, sleep problems, and altered hormone secretion

true or false: there are no known cognitive disorders linked to epithalamus

true

what is subthalamus

small ventral part of diencephalon containing subthalamic nucleus

function of subthalamic nucleus

connects functionally to the basal ganglia and helps regulate motor control

diagram of parts of diencephalon

what are the basal ganglia

group of nuclei located at base of forebrain that regulate voluntary movement, learning, behaviour and emotion

where are the basal ganglia located

at the base of the forebrain, deep within the cerebral hemispheres

what are the main functions of basal ganglia

help control voluntary motor movements, routine behaviors, procedural learning, eye movements, and emotional processing

how do the basal ganglia communicate with other parts of the brain

they form loops with the cortex and thalamus—receiving input from the cortex, processing it, and sending feedback via the thalamus to guide movement selection

why are these loops between the cortex, basal ganglia, and thalamus important

they help the brain choose and execute the most appropriate voluntary movements while inhibiting unnecessary ones

what is the striatum, and what does it do

main input area of the basal ganglia that receives signals from the cortex and responds to rewarding, aversive, or novel stimuli

what are the main components of the basal ganglia

• striatum

• globus pallidus

• substantia nigra

• subthalamic nucleus

how are the structures of the basal ganglia connected

linked in highly specific pathways that together regulate motor control systems outside the basal ganglia

what happens when the basal ganglia are damaged

• tremors

• involuntary muscle movement

• abnormal posture or muscle tone

which movement disorders are linked to basal ganglia damage

• parkinson’s disease

• huntington’s disease

• dyskinesias

which cognitive disorders are associated with basal ganglia dysfunction

• depression

• schizophrenia

what is the nucleus accumbens

component of the basal ganglia involved in the brain’s reward system

main function of nucleus accumbens

to make you feel pleasure or reward from certain experiences and motivate you to repeat them

how does the nucleus accumbens relate to drugs and addiction

mediates the effects of many psychoactive and addictive drugs that activate the brain’s reward pathways

what happens if nucleus accumbens are damaged

can cause behavioral impairments and affect motivation and reward processing

which disorders are associated with nucleus accumbens dysfunction

• addiction

• depression

• schizophrenia

why is nucleus accumbens important for behaviour

helps reinforce behaviors by linking actions to feelings of pleasure or satisfaction, driving learning and motivation