Hippocampus & Memory Flashcards
What is memory?
Cognitive function that allows us to encode, store and retrieve experience and info
Memory systems
Short term (operative)
Long term (implicit and explicit)
Implicit memory
Can not be verbalized
- PRS
- Procedimental learning
- Conditioning
Perceptual representation system (PRS) - characteristics
Subconscious sensory learning
Not affected by age or neurodegeneration
Automatic
Long duration
Independent from processing level
Influenced by perceptual aspects
Perceptual representation system (PRS) - localization
Occipital lobe (visual)
Perisylvian cortex (auditory)
Procedimental learning
Learning motor behaviours and motor skills by training
Procedimental learning - localization
Basal ganglia, cerebellum, premotor and motor cortex, amygdala,…
Explicit memory
Acquired by reading or through explanation
- Semantic memory
- Episodic memory
Semantic memory
Acquisition (verbal or visual) of concepts, word meanings & general knowledge.
Semantic memory - characteristics
Not linked to acquisition context
Semantic memory - localization
Tertiary sensory cortex - associative cortex
(Stored around the whole of the brain but it has to pass through hippocampus)
Episodic memory
Storage of life experiences. Auditory and visual.
Episodic memory - characteristics
Linked to acquisition context
High diagnostic yield
Episodic memory - localization
Prefrontal cortex
Limbic system (emotions)
Operative memory - characteristics
Retain verbal and spatial info
Retrieve and activate info from long term memory
Recruit congnitive sources
Aids in attention
If distracted, they disappear
Operative memory - localization
Frontal, parietal, perisylvian and occipital cortex
Operative memory - subsystems
Central executive (directs attention)
Phono-logical loop (words & numbers by repeating them)
Visuospacial sketch pad (localizat & visual characteristics of an object)
Memory system delopment
1º PRS
2º implicit memory
3º explicit memory
Memory processes
1º stimulus —> record it
2º encode the info (put the info in context of previous info)
3º info is stored (enters long-term memory)
4º to remember: retrieve the info
(5º consolidation: fix into our minds —> sleep)
Two main structures involved in encoding, consolidation and storage
Prefrontal cortex —> working memory
Hippocampus —> explicit memory storage
Cellular and molecular mechanism of explicit memory in prefrontal cortex
Working memory requires persistent neural act in here
- at a single neuron level: keep firing
- at a circuit level: form a loop
Cellular and molecular mechanism of explicit memory in hippocampus
Long-term explicit memory consolidation depends on synaptic circuits in the hippocampus.
It begins and ends at Entorhinal cortex:
- Entorhinal cortex -> CA1 -> subiculum -> cortex
- Entorhinal cortex -> dentate n -> CA3 -> CA1 -> subiculum -> cortex
Hippocampus is located in
Deep temporal lobes
Hippocampus proper
CA1, CA2, CA3 and CA4
Hippocampal formation
Hippocampus proper
Dentate gyrus (related to hippocampus but not part of hippocampus itself)
Subiculum
Have 3 layers
Hippocampus and dentate nucleus
Has 5 layers
Entorhinal
In the hippocampus info is
Encoded
Stratus Alveus
4th later in the hippocampus, formed by the fimbriae, that will form the fornix
Fornix
Source of output and input for the hippocampus (serotonine, NA, Ach, dopamine)
Long term potentiation (LTP)
Processes involved in storing info for a long time (in hippocampus)
Long term potentiation (LTP) - common features
- Neural mechanisms at a monosynaptic level
- Make synapses stronger (remembering)
- NMDA receptors (ionic channels that work on glutamate)
Long term potentiation (LTP) - variations
Presynaptic potentiation = more neurotransmitters
Postsynaptic potentiation = more receptors
Early LTP
Increase the number of receptors or increase NT
Fast mechanisms
Allows storage for hours
Late LTP
Act on transcription factors, … —> new receptors, additional synaptic connections (epigenetic changes, acting on DNA)
Memories for a very very long time (support implicit and explicit memory)
