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Chapter 5

Chapter 5

12 Pages
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Department
Physiology
Course Code
PSL440Y1
Professor
A

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Chapter 5 Encoding and Retrieval from Long-term Memory The Nature of Long-Term Memory Memory is the internal repository of stored information and guides our behaviour Memory relies on a set of processes by which information in encoded, consolidated and retrieved Long-term memory comprises of information that is acquired in the course of an experience and that persists so that it can be retrieved long after that experience is past Long-term memory can be consciously retrieved so and we can direct our behaviour using our previous experiences Long term memory can also influence our present thinking and behaviour while operating outside awareness past experience can unconsciously affect the present The Forms of Long-Term Memory There are multiple forms of long term memory that differ in their basic information processing properties and in the brain structures supporting them. Declarative memory (explicit memory) refers to a form of long-term memory that can be consciously recollected and declared or described to other people such as memories of facts, ideas and events. Declarative memory includes two types of memories: i. Episodic memory; the memory of events in our own personal past. It is the conscious knowledge that is temporally dated and spatially located. Such type of memory has a context e.g. meeting a friend in a room ii. Semantic memory; our general knowledge about things in the world and their meaning. It is the knowledge of words and concepts, their properties and their interrelations. This type of memory is not context bond because we acquire the knowledge across multiple experiences in a variety of contexts. Tests that assess declarative memory are termed explicit memory tests because they require the retrieval of an explicit description or report of knowledge from memory. Declarative memory is highly flexible and involves the association of multiple pieces of information and integrates them together to form a unified representation Declarative memory depends on the operation of medial temporal lobes Non-declarative memory (implicit memory) refers to non-conscious forms of long- term memory that are expressed as a change in behaviour without any conscious recollection. Tests of non-declarative memory called implicit memory tests do not require the description of the contents of memory but rather reveals the memory implicitly by changes in performance. Non-declarative memory is more restricted in the ways that it can be retrieved The different forms of implicit memories e.g. habituation/conditioning/learning of skills operates on different regions of brain The Power of Memory: The Story of HM 1 Information about memory comes to a large extent from a patient HM who underwent bilateral removal of medial temporal lobes (included hippocampus, amygdala) and suffered from a memory loss, but his working memory was intact Working memory is composed of information that in maintained over a period of seconds or minutes and it does not depend on medial temporal lobe structures HM also has preserved episodic and semantic memory of information acquired before his operation HM suffered from severe anterograde amnesia; the inability to consciously remember information encountered after brain damage. As soon as the information acquired disappeared from his working memory, he almost completely forgot it. This forgetting reveals an inability to form, retain or retrieve new episodic memories. HM was frozen in time i.e. he was unable to update his personal life narrative because of the inability to remember daily experiences. This amnesia is the failure to remember new events regardless of the content or modality i.e. failure to form episodic and semantic memory HM also demonstrated some retrograde amnesia; the forgetting of events that occurred before brain damage. This amnesia was temporally graded; the closer an event occurred to the surgery, the more likely it was forgotten. This pattern of forgetting suggests that memories do not permanently depend on the medial temporal lobes, otherwise HM would have forgotten early memories too. It indicates that over time, memories become strong even after damage to medial temporal lobes Multiple Memory Systems for Long-Term Learning and Remembering Medial temporal lobes are not necessary for all types of long-term memory because HM was able to acquire new motor skills at a normal rate e.g. HM was able to remap the visual perception onto motor actions Non-declarative memories (implicit memories) that operate outside our awareness are preserved despite damage of medial temporal lobe Amnesic patients demonstrate normal priming effects when they are asked to complete a word by using the first word that comes to their mind but if asked to complete a word by recalling the word they previously heard, they encounter more difficulty Amnesic patients are also able to improve their performance on perceptual and conceptual tasks but they lack the episodic memory of it Encoding: How Episodic Memories are Formed? Encoding is the term used for various processes by which information is transformed into a memory representation. These processes are set in motion at the time of the experience and form a mental representation by recording some aspects We can uncover the properties of encoding by determining the factors that strengthen encoding of information Encoding is influenced by degree to which we attend to the information and the extent to which we elaborate on its meaning 2 Elaboration involves interpreting information, connecting it with other information and reflecting on it. Other influences that strengthen encoding are conscious retrieval of information and practicing the information by spacing it out in time. Medial temporal lobes play a critical role in episodic encoding The Importance of Attention Forgetting is a neural consequence of ineffective coding of an experience into episodic memory Poor encoding often occurs when we fail to attend to an event; attention may be divided Frontal lobes support the ability to attend during learning and affect episodic encoding Levels of Processing and Elaborative Encoding Intent is required for effective memory formation but its only important because the intent to encode can motivate attention Encoding is an automatic by-product of attending to and processing a stimulus, the critical point if how we process the stimuli and not why we do it Levels of Processing Theory: Arguments and Limitations Levels of processing theory draws on the fact that there are various aspects of any given stimulus that can be attended and processed. In this view, encoding is a by- product of stimulus processing; when we process a stimuli it leaves a residue in the system that can guide later remembering of information. Different aspects of stimulus processing correspond to d
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