Limbic System: Manaye Flashcards
List the brain structures associated with the limbic system.
- involve motor and nonmotor areas that will integrate your learning, memory, and emotions
- all the animals mate through pheromones
- smell is important to like your food or stay in certain environments
Amygdala Entorhinal cortex Hippocampal formation Cingulate gyrus & cingulum Hypothalamus Thalamus Septum
What is the entorhinal cortex and what structures in the brain is it closely related to?
it is part of the limbic system
- located in the anterior part of the parahippocampal gyrus, on the medial surface of the temporal lobe
- transition zone between hippocampus and temporal neocortex
- multiple inputs to the entorhinal cortex, including fibers from the cingulate gyrus, basolateral amygdala, olfactory cortex, and cortical association areas
-entorhinal cortex funnels highly processed cortical information to the hippocampal formation and serves as its major output pathway
How are all the limbic structures connected?
through long term potentiation (Allard’s lecture)
CA1-4
The hippocampus is composed of two major components, the dentate gyrus and the hippocampus proper – the latter also referred to as Ammon’s horn or cornu Ammonis (CA regions). The Ammon’s horn region is divided into four subregions – area CA4 or the hilus, areas CA3, CA2, and CA1.
What is learning and what are the routes in which it occurs?
- is the acquisition of new experiences (information)
- strengthen of receptors and synapses
-can be achieved through plasticity, associative and Non-Associative learning
How strong must a stimulus be for an individual to learn?
it depends on the individual and ???
What is the function of the limbic system?
It is the system controlling learning, emotion, motivation, and memory in man. It has two parts; cortical and subcortical components.
- drives and rewards, crucial to motivational state
- affects visceral activities central to emotional expression
- influences sensory and associative mechanisms that are critical ingredients of perceptions and perhaps thought
Where is the majority of the limbic system located?
around the rim of the lateral ventricle
What is the role of the Paul McLean (1949) in the limbic system?
expanded on the Papez circuit in the article “Psychosomatic Brain and the Viscera
What is the role of the Papez (1930) in the limbic system?
Linked the structures comprising the “Limbic System” as having a role in emotions.
What is the role of the Broca (1878) in the limbic system?
“Le Grande Lobe Limbique” (Grand Limbic Lobe) – this is a reference strictly to anatomical organization
What is the rhinencephalon?
part of the brain associated with the olfaction
What is the hippocampal formation?
- it is closely associated with the adjacent dentate gyrus and forms an S-shaped structure
- consists of the dentate gyrus, hippocampus proper, and the subiculum
- each of these components have 3 layers of neurons
- embryologically the hippocampal formation is an extension of the medial edge of the temporal lobe
Where is the dentate gyrus located?
occupies the interval between the hippocampus and parahippocampal gyrus
What is the subiculum?
the part of the parahippocampal gyrus that is in direct continuity with the hippocampus
Describe the anatomy of the hippocampal formation.
- part of the limbic system
- located in the temporal lobes
- composed of dentate gyrus, CA1-3, and subiculum
- perforant pathway
What is the perforant pathway and what is its function?
- provides a connectional route from the entorhinal cortex to all fields of the hippocampal formation, including the dentate gyrus, all CA fields (including CA1), and the subiculum
- perforant activates the Ca3 neurons in the hippocampus which is important for encoding memory
What is the histology of the limbic system? What are the layers of the hippocampus?
- cortical structure of parahippocampal gyrus is six layers
- as the cortex is traced into the hippocampus there’s a gradual transition from a six to three layered arrangement
the hippocampus has:
- outer molecular layer
- middle pyramidal layer
- inferior and inner polymorphic layer (CA1, CA2, CA3, and CA4 (cornu Ammonis)
Describe the distribution of hippocampal neurons.
- cluster of neurons entering the dentate gyrus known as CA1-CA4 are pyramidal cells
- neurogenesis only occurs in the dentate gyrus within the limbic system
- most of the neurons in the dentate gyrus are granular cells
What is long term potentiation?
- increased excitability during altered chemical state on repeated stimulation of synapses
- is due to augmentation of postsynaptic potentials overtime
What is the fundamental postulate of the molecular mechanisms of memory storage?
anatomical connections between neurons
-these mechanisms are set by genetics and the strength and effectiveness of synapses
Is memory predetermined?
NO but it can be altered by experiences
What are the neural mechanisms of learning?
?????
What is learned (where in the brain; organization level?
???
What is perceptual learning?
functions to identify objects and situations
What is stimulus-response learning?
involves making a response when a particular stimulus is present as
- classical conditioning
- operant conditioning
What is motor learning?
involves forming new circuits in the motor system
What is relational learning?
involves identifying connections between stimuli
What are associated with associative and non-associative learning?
associative:
- classical conditioning
- operant conditioning
non-associative
- habituation, sensitization
- perceptual in nature
- recognition of objects and situations
Which type of learning involves acquisition of new motor behaviors, associations between new stimuli and existing behaviors, and new associations between familiar stimuli and existing responses?
associative learning
What is habituation in non-associative learning?
- repeated exposure to a stimulus results in REDUCED responding to that stimulus
- generally neutral, non-noxious stimuli
What is sensitization in non-associative learning?
- repeated exposure to a stimulus results in INCREASED responding to that stimulus
- generally biologically relevant, strong hedonic valence (positive or negative)
- also refers to augmentation of responding following exposure to a second stimulus
What are the 3 pathways in the hippocampal formation that display long term potentiation?
- perforant pathway (subiculum to dentate gyrus)
- Mossy fiber pathway (dentate gyrus to CA3 pyramidal cells)
- Schaffer collaterals (CA3 pyramidal cells to CA1 pyramidal cells)
What is memory?
an active system that receives information from the senses, organizes, and alters it, stores it away, and then retrieves the information from storage
What are the different processes of memory?
encoding: the set of mental operations that people perform on sensory information to convert that information into a form that is usable in the brain
storage: holding onto information for some period of time
retrieval: getting information is in storage nto a form that can be used
What are the 3 gross stages of learning and memory?
- acquisition
- storage
- retrieval
- Incoming sensory information will go to sensory buffers and get encoded
- they will then procede to the either be placed in short-term or long-term memory which are both consolidated through repetition or training of your neurons to learn and remember that activity
What is the importance of CA1?
it is a target of epileptic seizures
CA3 is innervated by what pathway?
perforant pathway
Which fibers go to the neocortex?
fornix
What are the brains structures involved in memory?
- prefrontal cortex
- amygdala
- medial temporal gyrus
- hippocampus
- cerebellum
What is the function of the following brain structures in regards to memory?
- prefrontal cortex
- amygdala
- medial temporal gyrus
- hippocampus
- cerebellum
- prefrontal cortex: memory involving the sequence of events, but not the events themselves
- amygdala: encodes emotional aspects of memory
- medial temporal gyrus: (not visible) encodes and transfers new explicit memories to long-term memory
- hippocampus: encodes and transfers new explicit memories to long-term memory
- cerebellum: memory involving movement
What brain structure is associated with working memory?
prefrontal cortex
What brain structure is associated with explicit memory that involves episodic (remembering events) and semantic (knowing facts) memory?
hippocampus, nearby cortical areas, medial diencephalon
What brain structure is associated with implicit memory specifically related to skills and habits? ?
striatum, motor areas of cortex, cerebellum
What brain structure is associated with implicit memory specifically related to emotional assoications?
amygdala
What brain structure is associated with implicit memory specifically related to conditioned reflexes?
cerebellum
What are the two types of declarative long term memory?
declarative: things you know that you can tell others
episodic: remembering your first day in school
semantic: knowing the capital of France
What are the three types of nondeclarative (procedural) long term memory?
nondeclarative (procedural): things you know that you can show by doing
- skill learning: knowing how to ride a bicycle
- priming: being more likely to use a word you heard recently
- conditioning: salivating when you see a favorite food
Why do we forget? What is encoding failure and what are the factors that can cause it?
- naturally our brain goes through an unknown process that makes room for new memories
- encoding failure- failure to process information into memory
Pathologically:
- amnesia
- dementia
What is the difference between anterograde and retrograde amnesia?
anterograde: -inability to establish new memories
- loss of relational learning ability
- New declarative memories are not formed
- Simple stimulus-response, perceptual and motor learning abilities remain intact
- Previously formed memories remain intact
retrograde: inability to recall past memories
- loss of previously formed declarative memories
What is infantile amnesia?
Childhood amnesia, also called infantile amnesia, is the inability of adults to retrieve episodic memories (memories of situations or events) before the age of two to four years, as well as the period before the age of ten of which adults retain fewer memories than might otherwise be expected given the passage of time.
What is dementia/
Dementia is not a specific disease. It’s an overall term that describes a group of symptoms associated with a decline in memory or other thinking skills severe enough to reduce a person’s ability to perform everyday activities. Alzheimer’s disease accounts for 60 to 80 percent of cases.
What is the memory deficiency caused by lack of thiamine (vitamin B6) that is often seen in chronic alcoholism? What areas of the brain are affected? What are some of the symptoms of patients suffering from this syndrome?
Korsakoff’s syndrome
- brain damage occurs in mammillary bodies of the hypothalamus and basal frontal lobes, which produces anterograde amnesia
- disconnects the path between the hippocampus anterior thalamic nucleus
- causes memory impairment
- patient often fabricate imaginary experiences as compensation for loss of memory (confabulate); fill in a gap in memory with a false memory that they fully believe to be true
What are some emotions associated with behavioral stress?
approach
withdrawal
What are some emotions associated with motivational stress?
reward punishment thirst hunger pain craving
What are some emotions associated with moods and background emotions?
depression anxiety mania cheerfulness contentment worry
What are some emotions associated with emotion systems?
seeking
panic
anger
fear
What are some emotions associated with basic emotions?
happiness fear rage disgust sadness surprise contempt admiration jealousy
What are some emotions associated with social emotions?
pride embarrassment quilt shame maternal love sexual love infatuation
What is the feed-forward mechanism that can induce specific emotion?
emotion generates an emotional response in the person via connections to the motor structures, hypothalamus, and brainstem nuclei (where emotional response is generated)
The emotional state in the person perceiving the stimulus is through activation of what parts of the brain?
right somatosensory cortices
What is the anatomy of the cingulate gyrus?
- the cingulate gyrus wrap around the external border of the corpus callosum, warping around its genu (subcallosal gyrus)
- there is a posterior, anterior, and medial part as it is a rim
- receives inputs from the thalamus and the neocortex
- projects to the entorhinal cortex via cingulum
What area of the brain is associated with disgust?
frontal insula
What are the functions of the cingulate gyrus?
- emotion formation and processing
- memory-learning
- related to pain sensory
What are disorders related to cingulate gyrus?
- depression
- schizophrenia
What are mirror cells? Where do they reside and what is their function?
- A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action performed by another. Thus, the neuron “mirrors” the behavior of the other, as though the observer were itself acting.
- resides in the insula and anterior cingulate gyrus
- mediates empathy: the experience of feeling the emotion of another
What are the 6 layers of the neocortex (cortical structures of the limbic system)?
- entorhinal cortex
- parahippocampal gyrus
- hippocampus
- amygdala
- cingulate gyrus
- olfactory cortex
What are the parts of the diencephalon? (subcortical structures of the limbic system)?
- thalamus: anterior nucleus (gets reciprocal input) AND mediodorsal nucleus
- hypothalamus: medial and mammillary bodies
The limbic cortex consists of what two structures?
cingulate gyrus: dorsal to the corpus callosum and is heavily interconnected with the associated areas of the cerebral cortex; consists of an anterior and posterior cingulate gyrus; involved in planning of info related to pain, anger or sadness; it also involves the premotor cortex for planning
parahippocampal gyrus: in the medial temporal lobe and contains several distinct regions, the most important being the entorhinal cortex; consists of a large number of neurons from hippocampal, dentate, and subiculum gyrus
What is the difference between anterior and posterior cingulate gyrus?
- anterior receives input from anterior and dorsomedial thalamus and neocortex and projects back to ERC via cingulum and goes through hypothalamus
- anterior cingulate gyrus works with amygdala for immediate action to run away from something that you fear??
What are the only thalamic nuclei related to emotions?
anterior and dorsomedial thalamic nuclei
What is important about the cingulate gyrus?
- is also related to motor
- you are so sad that you cannot move your arms
- facilitates negative memory (pain, anger, depression)
associated with autonomic system (gets projections from lateral hypothalamus and inferior gyrus important for hunger, trust, pain)
Explain the relationship between the amygdala and anterior cingulate gyrus.
- they work hand in hand
- amygdala is involved in fear perception, ANS response and memory
- anterior cingulate gyrus stores that memory and retrieves it whenever necessary (retrieves memories that are unpleasant and painful)
- all the noises associated with pain is through the activation of the anterior cingulate gyrus and amygdala
-amygdala activation by fearful stimuli and fearful faces
The hippocampus layers is comprised of what neurons?
CA1
CA2
CA3
CA4
Most of the neurons in the dentate gyrus are what kind of cells?
granular cells
What is the difference between neurogenesis and neuroplasticity?
- neurogenesis is born of new cell
- neuroplasticity is when a surviving cell is learning how to function like a normal cell and extend its processes and strengthen its synapses
Where in the hippocampal formation is there neurogenesis?
dentate gyrus
What is the papez circuit?
AKA limbic circuit is a neural circuit for the control of emotional expression
hippocampal formation (subiculum)–> fornix—> mamillary bodies —-> mammilothalamic tract—-> anterior thalamic nucleus–> cingulum–> hippocampal formation
basic neural circiut through -perforant activates the Ca3 neurons in the hippocampus which is important for encoding memory
-all the information will be taken up by the Mossy fibers which are glutaminergic and project to subiculum via fornix back to the diencephalon specifically the mammillary bodies and anterior nucleus of the thalamic
Why is the Papez circuit important?
learning and emotions involve both motor and higher cortical functions through basal ganglia for motor learning
long term potentiation occurs which will stimulate your axons and connectivity
circuit is greatly influences by the cerebellum and lesions of the cerebellum can have an inhibitory effect on the circuit
