Biopsychology of declarative memory Flashcards
What is the hippocampus?
Brain region in the medial temporal lobe. It has a very complicated shape because it is folded in one dimension and curved in another.
Is the first brain structure that has been specifically associated with long-term memory.
Define the term anterograde and retrograde amnesia.
Neuropsychological condition characterized by an impairment of retrieving memories about events happened before (retrograde) or after (anterograde) the brain lesion.
Define the term long-term potentiation and depression.
Cellular mechanisms associated with learning.
What are the two levels that occur from changes to the nervous system due to learning?
Gross Level
Cellular Level
What is gross level?
➢ Changes in brain structure occurring over time, for example, experienced London taxi drivers have larger hippocampi than controls (Maguire et al., 2000, PNAS).
➢ Changes in brain function, for instance, changes in brain activation or neural connectivity during a memory task or during consolidation.
What does lesions in the hippocampus induce?
Amnesia
What is amnesia?
Chronic impairment of memory encoding or retrieval. In neurodegenerative diseases, amnesia is slow and progressive. In other cases, the impairment follows a traumatic event. There are two types of amnesia: anterograde amnesia involves a failure to remember events after the traumatic experience (e.g., new memories). Retrograde amnesia involves a failure to remember events before the trauma.
What do studies on patients with amnesia provide?
One of the strongest evidence in favour of a multi-component view of long-term memory.
Usually patients have impairments in declarative memory, especially episodic memory, but not in other types of memory.
What happened to HM?
HM had a bilateral medial temporal lobectomy (meaning that he had most portion of his hippocampus, parahippocampus and amygdala surgically removed on both hemispheres) to treat his epilepsy. After the surgery, he did not have seizures anymore but he was left with a severe anterograde amnesia.
Explain HM’s memory ability.
His short-term memory was unimpaired.
His procedural memory was unimpaired.
His semantic memory was relatively unimpaired.
His episodic memory for events that happened before the surgery was unimpaired (= he did not suffer from retrograde amnesia).
What was impaired in HM was his ability to form new memories (= anterograde amnesia).
What does the case of HM tell us about memory and the hippocampus?
❖ The hippocampus is not involved in short-term, semantic or procedural memory. HM could learn new procedures and could remember short-term relatively well. His semantic memory was relatively intact
❖ The hippocampus is not the location of (or it is not necessary for) long-term memories in general. HM could retrieve details from his past and events that happened prior to
the surgery. This suggests that the key role of the hippocampus is to learn and form NEW episodic memories.
❖ The hippocampus is responsible for explicit memory retrieval, but not for implicit memory retrieval. Some amnesic patients can store a record of an episode in their memory, although they are not able to explicitly retrieve that record, and/or to provide details of when or where they have acquired that memory.
Who did research on patient HM?
Scoville & Milner, 1957
Provide further investigations on patients with brain lesions who showed different patterns of memory impairments.
Patients with Korsakoff’s syndrome (lack of vitamin B1 due to alcohol abuse) develop similar memory impairments as those found in HM, but their hippocampus is intact. They have neuronal loss in the thalamus and hypothalamus.
Patients with similar lesions to HM develop different memory profiles. For instance, patient KC (Tulving, 1989) with bilateral hippocampal lesions suffered from retrograde as well as anterograde amnesia with no memory for remote events.
What are the discrepancies of investigations on patients with brain lesions?
Brain lesions in humans are never limited to specific parts of the brain but extend to neighbouring regions related to other cognitive functions. It is impossible to find two patients with exactly the same lesion!
More recent neuroimaging investigations using fMRI, EEG and brain stimulation suggest that episodic memory is associated with a network of brain regions, rather than with the activity of one single region.
What else is involved in learning brain activations?
Using fMRI, scientists have shown that during learning brain activations are not limited to the hippocampus, but also involve the parietal and prefrontal cortex (e.g., Schott et al., 2013, PNAS). These brain regions are functionally connected during learning.
