HNN Topic 6 - Limbic, Diencephalon, Attention/Learning/Memory Flashcards
List the types of attention
- Arousal
- Vigilance
- Divided attention
- Selective attention
Define vigilance and explain the effects of impaired vigilance
- Capacity to maintain attention for a prolonged period of time
- Impaired = impersistence (unable to correctly recall memory/thought)
What is the effect of breakdown of top-down regulation of attention?
Inattention, neglect (unaware of particular side of body, usually L)
Describe the location of the thalamus
- Walnut sized midline symmetrical structure, between the cerebral cortex and midbrain
- Surrounds the 3rd ventricle
Describe the location of the hypothalamus
- Inferior to the thalamus on either side of the third ventricle
- Sits inside the tracts of the optic nerve, just above the pituitary gland
Give examples of causes of hippocampal damage
HSV encephalitis, anoxia, early Alzeihmer’s
Define episodic memory
Personally experienced, temporally specific episodes/events
List the components of the epithalamus
Habenula, habenular commissure, stria medullaris, pineal gland
Describe the function of the anterior group of thalamic nuclei
Part of limbic system, controls mood
What is the effect of progressive R temporal lobe atrophy?
Prosopagnosia - behavioural disturbances (social disinhibition, hyper-religosity, aggressiveness)
List the components of the limbic system
- Hippocampus
- Hypothalamus
- Amygdala
- Mamillary bodies
- Anterior thalamic nuclei
- Olfactory bulbs
Describe the top-down regulation of attention and list the functional areas which it involves
- Conscious act
- Involves:
- Prefrontal cortex
- Parietal cortex
- Limbic cortex
Is attention a widespread or area-specific cognitive process?
- Both - widespread ‘global’ and domain-specific cognitive process
- Breakdown of global attention = delirium/acute confusional state
- Domain-specific attention relates to a specific sensory modality e.g. visual
- Breakdown of domain specific attention e.g. following a non-dominant hemisphere stroke = visual inattention
Describe the features of immediate (working) memory
- Part of attention/concentration
- Immediate recall of small amounts of verbal or spatial information
Define implicit (procedural) memory
Learned motor procedures, no conscious access - can’t be easily explained e.g. playing an instrument, riding a bike
What causes deficits in semantic memory?
Anterior temporal cortical destruction/atrophy, caused by:
- Herpes simplex encephalitis
- Trauma
- Tumours
- Alzheimer’s
- Semantic dementia
List the components of the diencephalon
- Thalamus
- Subthalamus
- Hypothalamus
- Epithalamus
Where is ARAS found and what is its function?
Located in the brainstem, involved in sleep/wakefulness
List the chronic causes of episodic impairment
Pure amnesia
- Hippocampal damage
- Diencephalic damage
Mixed amnesia
- Dementia
Describe the organisation of immediate (working) memory
- Central executive control - dorsolateral prefrontal cortex
- Moved to either:
- Visual sketchpad (spatial information) in the non-dominant parietooccipital lobe
- Phonologial store (words, numbers, melodies) in the dominant perisylvian language areas
How is the parietal cortex involved in top-down regulation of attention?
- Visual processing
- Posterior - basic shapes and colour
- Anterior - more complex
Describe the anatomical areas involved in semantic memory
- Limbic system involved in storage, maintenace and retrieval
- L hemisphere anterior temporal lobe - integrative region
- Anterior temporal cortex and angular gyrus
Describe the location of the diencephalon
Between the cerebrum and brainstem, surrounds the 3rd ventricle
List the acute causes of episodic impairment
Pura amnesia:
- Transient global amnesia
- Transient epileptic amnesia
Mixed deficit:
- Delirium
Describe the function of the ventral group of thalamic nuclei
- Ventral anterior nucleus - connects basal ganglia and motor cortex (movement)
- Ventral lateral nucleus - connects cerebellum/basal ganglia to motor cortex (movement)
- Ventral posterior nucleus - relays somatic sensation to cerebral cortex
- Lateral geniculate nucleus - visual information from optic tract to visual cortex
- Medial geniculate nucleus - auditory information from lateral lemniscus to auditory cortex
Define selective attention and explain the effects of impaired selective attention
- Ability to focus on one stimulus while suppressing other stimuli
- Impaired = distractibility
Describe bottom up regulation of attention
- Unconscious - quick response to danger, primitive
- Due to external factors
- Controlled by the ascending reticular activating system (ARAS)
- Limbic system also involved - close association with ARAS
Describe the causes and effect of breakdown of bottom up regulation of attention
- Due to metabolic disturbances or neurodegenerative disease
- Effect - impaired arousal/delirium
What is the function of the hypothalamus?
Through connections to limbic system, hippocampus, striatum and brainstem it regulates emotions, autonomic control, hunger/satiety, memory input, anger control and the sleep/wake cycle
How is attention tested in clinical practice?
- Orientation in time and place
- Serial 7s - count back from 100 in 7s
- Repeat series of digits/days of week/months backwards
Describe the function of the lateral group of thalamic nuclei
Connected to association areas/limbic system
List the parts of the thalamus
Made of 4 groups of nuclei, separated by Y shaped sheet of white matter - anterior, lateral medial and ventral groups
Define semantic memory
Factual information (general knowledge) and vocabularly, independent of context, time and personal relevance
Describe the function of the epithalamus
- Habenular nuclei - emotional response to olfaction
- Pineal gland - stimulated by hypothalamus to release melatonin, regulates sleep/wake cycle
- Connection between limbic system and other parts of the brain
Which anatomical areas are responsible for implicit (procedural memory)
Dependent on networks involving basal ganglia and cerebellum
Define arousal and explain the effect of impaired arousal
- General state of wakefulness/responsiveness
- Impaired = drowsiness
List the parts of the limbic cortex involved in top down regulation of attention
- Cingulate gyrus
- Hippocampus
- Fornix
- Amygdala
- Orbital and prefrontal cortex
- Mamillary bodies
How is the prefrontal cortex involved in top-down regulation of attention?
Dorsolateral prefrontal cortex - frontal eye fields, associated w/ motor cortex
What is the function of the hippocampus?
Involved in forming new memories
How is the hypothalamus attached to the pituitary gland?
Inferior portion of hypothalamus stretched into a hollow stalk which attaches to the pituitary
List the general functions of the limbic system
- Emotions
- Learning
- Influences formation of memory by integrating emotional states with stored memories of physical sensations
- Links smell and memory
- Exerts influence on endocrine and autonomic mervous systems producing both negative and positive emotional responses
What is the function of the amygdala?
Involved in the emotions of fear and aggression
What is the primary function of the limbic system?
Emotions and formation of memories
Describe the organisation of semantic memory
- Ventral –> dorsal = visual –> non-visual
- Posterior –> anterior = basic –> complex
Describe the location of the epithalamus
Posterior to 3rd ventricle, dorsal posterior segment of diencephalon
Describe the general function anatomy of attention control
Top-down regulation or bottom-up regulation
How is semantic memory tested in clinical practice?
- Tests of general knowledge + vocabulary
- Fluency - generate examples from specific semantic categories (e.g. name as many animals as possible in 60 seconds)
Define divided attention and explain the effects of impaired divided attention
- Ability to respond to more than one stimulus at once
- Impaired = distractibility
Give examples of causes of diencephalic damage
Korsakoff’s syndrome, bilateral thalamic stroke, post sub-arachnoid haemorrhage
Describe the structure and location of the amygdala
Two almond shaped masses of neurons on either side of the thalamus at the anterior aspect of the hippocampus
Describe the classifications of memory
- Memory divided into long-term and immediate (working)
- Long-term divided into explicit (declarative) and implicit (procedural)
- Explicit includes episodic and semantic
- Implicit includes motor skills and classical conditioning
Describe a deficit in implicit (procedural) memory
Profound amnesia can occur e.g. Korsakoff’s syndrome
Describe the location of the hippocampus
Gyrus running medially along the temporal lobe, two horns curving back from the amygdala
Describe the anatomical areas involved in episodic memory
Extended limbic system (circuit of Papez)
- Medial temporal lobe - hippocampus + entorhinal complex
- Diencephalon - mamillary bodies + thalamic nuclei
Dorsolateral prefrontal cortex
- Temporal organisation, interacts w/ structures within extended limbic system
Describe the location of the limbic system
Lies on both sides of the thalamus, just under the cerebrum
Define attention
Process of selecting most relevant information quickly, while filtering out less relevant information in order to be able to respond quickly
Describe the general function of the thalamus
Relay centre
Describe transient global amnesia
- Most common in middle aged people
- Unable to form new memories during episodes - last a few hours
- Cause unclear - vascular?
Define explicit (declaritive) memory
Memories available to conscious access + reflection
How is episodic memory is tested in clinical practice?
- Recall of complex information (Wechsler memory scales)
- Word-list learning (California verbal learning test)
- Recognition of newly encountered words + faces (Warrington’s recognition memory test)
Describe the function of the medial group of thalamic nuclei
Emotions, connected to prefrontal cortex
