Week 5 - Brain Networks Flashcards
The Brain - Lobes
Lobes of the cortex
Parietal
Occipital
Frontal
Temporal
Cerebellum
The Brain - Orientation
Dorsal/superior (top)
Caudal/posterior (back)
Ventral/inferior (bottom)
Rostral/anterior (front)
Axial (in half parallel to the floor)
Sagittal (in half parallel to the nose)
Coronal (in half parallel to the shoulders)
The brain - sulci & gyri
SFS, IFS, SFG, MFG, IFG, STS, ITS, STG, MTG, ITG
SFS, IFS, SFG, MFG, IFG, STS, ITS, STG, MTG, ITG
S= superior I = Inferior M= Middle F= Fontal T= Temporal S= Sulcus G = Gyrus
Neuron
Basic unit of the nervous system
Specialised cell that transmits neural impulses to other neurons, glands or muscles
Three types:
- sensory neurons: sends impulses received by the receptors to the brain
- Motor neurons: sends outgoing signals from brain to the muscles and glands
- Interneurons: connects sensory (afferent) and motor (efferent) neurons
Glial cells: Outnumber number of neurons in the brain and support the function of neurons. Different types
Neuron
Action potentials
Resting electrical potential of a Neuron
Excitation threshold
Action potentials: electrochemical impulse that travels from the cell body down to the end of the axon as a result of electrically charged molecules (ions) travelling in and out of the neuron
Resting electrical potential of a neuron: -70mV
- Electrical potential across cell membranes will change if stimulated by other neurons
- Stimulation caused by action of neurotransmitters that are released by presynaptic neuron and received by postsynaptic neuron
Excitation threshold: -50mV
-depolarisation: temporary reversal of electric potential across the membrane (all-or-none law)
Neuron
How it works
Neurons receive chemical signals on branches called dendrites
When a neuron is depolarised above it’s excitation threshold, it generated an all-or-none action potential
Neurons transmit electrochemical impulses (action potentials) down the axon
The action potential initiates the release of neurotransmitter at the terminal buttons
Chemical neurotransmitters are released at synapses and carry messages between two neurons
Neurotransmitters exert their action by binding to receptors
Neuron
Multiple sclerosis (MS)
Amyotrophic lateral sclerosis (ALS)
Multiple Sclerosis (MS) Damage to insulating covers of nerve cells (myelin) in the brain and spinal cord
Amyotrophic lateral sclerosis (ALS)
Progressive degeneration of the motor neurons
Brain
Classification based on function
- Central core (regulates involuntary and primitive behaviours)
- Limbic system (regulates emotions)
- Cerebrum (regulates higher intellectual processes)
Brain: Hindbrain
Medulla oblongata
Pons
Reticular formation
Cerebellum
Medulla oblongata: breathing, posture reflexes
Pons: timing of sleep, attentiveness
Reticular formation: arousal, awareness
Cerebellum: coordination of movement, coordination of higher mental functions
Brain: Midbrain
Superior colliculus & inferior colliculus
Substantia nigra
Superior colliculus & inferior colliculus: relaying sensory information to the brain, movement control
Substantia nigra: crucial part of the reward pathway of the brain, movement
Brain: Forebrain
Thalamus Hypothalamus Pituitary gland Limbic system Amygdala Hippocampus
Thalamus: sensory relay station (directing information from sense receptors to cerebrum
Hypothalamus: eating, drinking, sexual behaviour, homeostasis, sensation of emotions, stress response
Pituitary gland: part of endocrine system - production of hormones
Limbic system: controls some instinctive behaviours to allow for some degree of flexibility, emotional behaviour
Amygdala (limbic): Emotions - especially fear
Hippocampus (limbic): Memory
Brain Networks
Central executive network (CEN)
CEN:
Cognitive control network. Task positive network
The fronto-parietal task control network responsible for higher-level cognitive functions, including the control of attention and working memory
Key areas:
i) lateral prefrontal cortex
ii) dorsal anterior cingulate
iii) posterior parietal cortex
iv) basal ganglia
v) cerebellum
Brain networks
Default mode network (DMN)
DMN:
Resting brain network. Task negative network
A large-scale network of brain areas that form an integrated system for self-related cognitive activity, including autobiographical, self-monitoring and social functions.
Key Areas:
i) medial prefrontal cortex
ii) posterior cingulate cortex
iii) lateral temporal cortex
iv) inferior parietal cortex
v) hippocampus
Brain networks
Salience Network (SN)
Monitors the relevance of external inputs & internal bodily experience
The SN is situated at the interface of the cognitive, homeostatic, motivational, and affective systems of the human brain. It plays a crucial role in identifying the most biologically and cognitively relevant endogenous and external stimuli in order to adaptively guide behaviour
Key areas:
i) insula
ii) anterior cingulate cortex (ACC)
Brain networks
Three intrinsic connectivity networks in the human brain have been identified as central to the understanding of higher cognitive function: the central executive, salience and default mode networks. The responses of these networks generally increase and decrease proportionally and antagonistically during cognitive tasks.
The central executive network is a frontoparietal network that is crucial to working memory and cognitive control of thought, emotion and behaviour.
The salience network consists of the dorsal anterior cingulate cortex and the frontoinsular cortex and is involved in the detection of personally salient internal and external stimuli to direct behaviour with the goal of maintaining homoeostasis
The default mode network, which consists of cortical midline structures and lateral parietal lobes, plays an important part in self-related processes, emotion regulation, social cognition, autobiographical memory and future-oriented thinking
Crucially, the anterior insula (salience network) is thought to mediate the dynamic interface between externally oriented attention and internal self-reflective functioning, mediating switching between engagement of the central executive network and disengagement of the default mode network and facilitating engagement of brain areas mediating attention, working memory and higher-order cognitive processes.
Disrupted networks in clinical disorders
Salience network
Clinical markers:
Hyperarousal or hypoarousal
Anterior insula facilitates switching between default mode and central executive network
Default mode network
Clinical markers:
Self-referential processing
Central executive network
Clinical markers:
Executive dysfunction
Brain networks
Six major principles of large scale functional organisation
I. Nonrandom modular global brain architecture with strategic hub regions that regulate communication among different functional systems
II. strong interhemispheric connectivity between homotopic regions (E.G., between left premotor cortex and right premotor cortex)
III. The human brain is intrinsically organised into coherent functional networks with brain areas that are commonally engaged during cognitive tasks forming brain networks that can be readily identified using intrinsic functional connectivity
IV. Task and context-dependent activated and deactivated brain systems – bottlenecks in parallel processing and temporarally restricted access to neural resources
V. The most widely deactivated regions from a coherent large-scale network, the DMN, which is a tightly functionally and structurally connected system important for self-referential information processing and monitoring of the internal mental landscape
VI. Core prefrontal–parietal control systems can be dissociated into distinct brain networks with distinct roles in cognition.
Notably, the SN, is a system that plays an important role in attentional capture of biologically and cognitively relevant events while the lateral frontoparietal CEN, is important for the working memory and higher-order cognitive processes.
Paula is getting bored in the lecture and her mind drifts away as she thinks about the events of her last birthday and how much fun she had on the day
Which brain network is likely to be engaged in this context???
A) sensory motor network
B)salience network
C) central executive network
D) default mode network
D) default mode network
