Ribot's Law
Encyclopedia
Ribot's Law of retrograde amnesia
was hypothesized in 1881 by Théodule Ribot
. It states that there is a time gradient in retrograde amnesia, so that recent memories are more likely to be lost than the more remote memories. Not all patients suffering from retrograde amnesia
report the symptoms of Ribot's Law.
(1839 -1916), who is recognized as one of the pioneer 19th century advocates for psychology
as an objective and biologically-based empirical field. Ribot’s split from the mainstream “Eclectic” psychology of the era was associated with a transition from philosophical to evolutionary explanations of human psychology and behavior. As Ribot was not a true experimentalist himself, this increased focus on the natural science basis of human mentality was manifested in an interest for case studies and diseases of dysfunction which helped to shape theories of psychological function. Ribot’s Law actually was first defined in terms of a broad generalization of functional decline in psychopathology
: the observation that functions acquired most recently are the first to degenerate. However, in the current context of neuroscience
research, Ribot’s Law is used almost exclusively to describe the perceived effect of older memories being less prone to disruption.
In his 1882 book, “Diseases of Memory: An Essay in the Positive Psychology “, Ribot explained the retroactive phenomena of trauma or event-induced memory loss. Patients who incurred amnesia
from a specific event such as an accident often also lost memory of the events leading up to the incident as well. In the case of some, this retrograde
loss included several years leading up to the precipitating event of injury or trauma had occurred – yet left much older memories intact – suggesting that the effect was not just due to interference with consolidation of memories immediately before brain damage.
Other historical accounts supporting the greater strength of older memories include some studies of aphasia
starting as early as the late 1700s, in which bilingual patients recovered different languages with differential progress. In some cases, aphasics recover or preferentially improve only the first-acquired language, although this only seems to be the case mostly in people who were never truly fluent in their secondary language.
Currently, Ribot’s Law is not universally accepted as a supporting example for memory consolidation
and storage. As a component of the standard model memory of systems consolidation, it is challenged by the multiple trace theory which states that the hippocampus
is always activated in the storage and retrieval of episodic memory
regardless of memory age.
), and recollection
. Ribot’s Law states that following a disruptive event, patients will show a temporally graded retrograde amnesia
that preferentially spares more distant memories.
Experimental evidence largely confirms these predictions. In a study of electroconvulsive shock therapy patients, memories formed at least four years prior to treatment were unaffected, while more recent ones were impaired. An experiment with rats showed similar results. Rats were conditioned to fear stimuli in two different contexts: one 50 days before receiving hippocampal brain lesions, and the other 1 day before lesioning. Subsequently, they only showed fear memory in the 50-day old context.
Many neurological disorders, including Alzheimer’s disease, are also associated with a temporally graded retrograde amnesia, indicating that older memories are somehow strengthened against degeneration while newer memories are not. Although the mechanism for this strengthening is unclear, some models exist to explain the effects.
lead to the formation of a cortical trace which represents a single memory. While this MTH-neocortex interaction is initially required to maintain the memory trace, the model predicts that over time the importance of the MTH becomes diminished and eventually is unnecessary for the storage of the memory trace. The medial temporal hippocampus mediates memory formation by maintaining the connections between various neocortical regions that make up each memory trace. At first the associations between neocortical areas that make up a newly formed memory trace are weak, however repeated activation of these areas in succession lead to “consolidation” of the trace within the neocortex. Once consolidation is sufficiently complete, the memory trace becomes mediated through neocortical activity alone and the MTH is no longer necessary for re-activation.
Figure 1 provides a visual explanation of the standard model. Initially, the memory trace (features of the experience represented by red circles) is weak in the neocortex and is reliant on its connections to the medial temporal hippocampal system (MTH) for retrieval. Over time, an intrinsic process results in the strengthening of the connections between memory trace representations in the neocortex. Since the connections are consolidated, the memory can now be retrieved without the hippocampus.
While never explicitly described by Squire and colleagues, the timescale of MTH-dependence in memory formation and maintenance is believed to vary by species as well as by the extent of hippocampal damage. For example, hippocampal lesion experiments with mouse models have shown retrograde amnesia for approximately one week prior to surgery, while case studies of human subjects with similar hippocampal damage have had retrograde amnesia limited to around two to three years prior to the accident).
The standard model of systems consolidation largely applies to the formation of declarative memories, which include semantic, factual memories and episodic
, autobiographical memories. This has been supported by case studies of human patients with MTH lesions who exhibit difficulties in remembering experiences and fact learned post-surgery, however are able to retain motor and skill memories such as how to ride a bike or perform mirror tracing tasks.
Retrograde amnesia
Retrograde amnesia is a loss of access to events that occurred, or information that was learned, before an injury or the onset of a disease....
was hypothesized in 1881 by Théodule Ribot
Théodule-Armand Ribot
Théodule-Armand Ribot , French psychologist, was born at Guingamp, and was educated at the Lycée de St Brieuc.In 1856 he began to teach, and was admitted to the École Normale Supérieure in 1862...
. It states that there is a time gradient in retrograde amnesia, so that recent memories are more likely to be lost than the more remote memories. Not all patients suffering from retrograde amnesia
Retrograde amnesia
Retrograde amnesia is a loss of access to events that occurred, or information that was learned, before an injury or the onset of a disease....
report the symptoms of Ribot's Law.
History and Context
Ribot’s Law was first postulated by the French psychologist Théodule RibotThéodule-Armand Ribot
Théodule-Armand Ribot , French psychologist, was born at Guingamp, and was educated at the Lycée de St Brieuc.In 1856 he began to teach, and was admitted to the École Normale Supérieure in 1862...
(1839 -1916), who is recognized as one of the pioneer 19th century advocates for psychology
Psychology
Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...
as an objective and biologically-based empirical field. Ribot’s split from the mainstream “Eclectic” psychology of the era was associated with a transition from philosophical to evolutionary explanations of human psychology and behavior. As Ribot was not a true experimentalist himself, this increased focus on the natural science basis of human mentality was manifested in an interest for case studies and diseases of dysfunction which helped to shape theories of psychological function. Ribot’s Law actually was first defined in terms of a broad generalization of functional decline in psychopathology
Psychopathology
Psychopathology is the study of mental illness, mental distress, and abnormal/maladaptive behavior. The term is most commonly used within psychiatry where pathology refers to disease processes...
: the observation that functions acquired most recently are the first to degenerate. However, in the current context of neuroscience
Neuroscience
Neuroscience is the scientific study of the nervous system. Traditionally, neuroscience has been seen as a branch of biology. However, it is currently an interdisciplinary science that collaborates with other fields such as chemistry, computer science, engineering, linguistics, mathematics,...
research, Ribot’s Law is used almost exclusively to describe the perceived effect of older memories being less prone to disruption.
In his 1882 book, “Diseases of Memory: An Essay in the Positive Psychology “, Ribot explained the retroactive phenomena of trauma or event-induced memory loss. Patients who incurred amnesia
Amnesia
Amnesia is a condition in which one's memory is lost. The causes of amnesia have traditionally been divided into categories. Memory appears to be stored in several parts of the limbic system of the brain, and any condition that interferes with the function of this system can cause amnesia...
from a specific event such as an accident often also lost memory of the events leading up to the incident as well. In the case of some, this retrograde
Retrograde
-Retrograde:* Retrograde motion, in astronomy, describes retrograde motions of celestial bodies relative to a gravitationally central object* Apparent retrograde motion, in astronomy, is the apparent motion of planets as observed from a particular vantage point...
loss included several years leading up to the precipitating event of injury or trauma had occurred – yet left much older memories intact – suggesting that the effect was not just due to interference with consolidation of memories immediately before brain damage.
Other historical accounts supporting the greater strength of older memories include some studies of aphasia
Aphasia
Aphasia is an impairment of language ability. This class of language disorder ranges from having difficulty remembering words to being completely unable to speak, read, or write....
starting as early as the late 1700s, in which bilingual patients recovered different languages with differential progress. In some cases, aphasics recover or preferentially improve only the first-acquired language, although this only seems to be the case mostly in people who were never truly fluent in their secondary language.
Currently, Ribot’s Law is not universally accepted as a supporting example for memory consolidation
Memory consolidation
Memory consolidation is a category of processes that stabilize a memory trace after the initial acquisition. Consolidation is distinguished into two specific processes, synaptic consolidation, which occurs within the first few hours after learning, and system consolidation, where...
and storage. As a component of the standard model memory of systems consolidation, it is challenged by the multiple trace theory which states that the hippocampus
Hippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...
is always activated in the storage and retrieval of episodic memory
Episodic memory
Episodic memory is the memory of autobiographical events that can be explicitly stated. Semantic and episodic memory together make up the category of declarative memory, which is one of the two major divisions in memory...
regardless of memory age.
Evidence
A large body of research supports the predictions of Ribot’s Law. The theory concerns the relative strength of memories over time, which is not directly testable. Instead, scientists investigate the processes of forgetting (amnesiaAmnesia
Amnesia is a condition in which one's memory is lost. The causes of amnesia have traditionally been divided into categories. Memory appears to be stored in several parts of the limbic system of the brain, and any condition that interferes with the function of this system can cause amnesia...
), and recollection
Recollection
Recall in memory refers to the retrieval of events or information from the past. Along with encoding and storage, it is one of the three core processes of memory. There are three main types of recall: free recall, cued recall and serial recall...
. Ribot’s Law states that following a disruptive event, patients will show a temporally graded retrograde amnesia
Retrograde amnesia
Retrograde amnesia is a loss of access to events that occurred, or information that was learned, before an injury or the onset of a disease....
that preferentially spares more distant memories.
Experimental evidence largely confirms these predictions. In a study of electroconvulsive shock therapy patients, memories formed at least four years prior to treatment were unaffected, while more recent ones were impaired. An experiment with rats showed similar results. Rats were conditioned to fear stimuli in two different contexts: one 50 days before receiving hippocampal brain lesions, and the other 1 day before lesioning. Subsequently, they only showed fear memory in the 50-day old context.
Many neurological disorders, including Alzheimer’s disease, are also associated with a temporally graded retrograde amnesia, indicating that older memories are somehow strengthened against degeneration while newer memories are not. Although the mechanism for this strengthening is unclear, some models exist to explain the effects.
The Standard Model of Systems Consolidation
Initially proposed in 1984 by Larry Squire, Neal Cohen, and Lynn Nadel, the standard model of systems consolidation is a contemporary theory used to explain the cognitive processes behind Ribot’s Law. In the model, interaction between the medial temporal hippocampus (MTH) and multiple areas in the neocortexNeocortex
The neocortex , also called the neopallium and isocortex , is a part of the brain of mammals. It is the outer layer of the cerebral hemispheres, and made up of six layers, labelled I to VI...
lead to the formation of a cortical trace which represents a single memory. While this MTH-neocortex interaction is initially required to maintain the memory trace, the model predicts that over time the importance of the MTH becomes diminished and eventually is unnecessary for the storage of the memory trace. The medial temporal hippocampus mediates memory formation by maintaining the connections between various neocortical regions that make up each memory trace. At first the associations between neocortical areas that make up a newly formed memory trace are weak, however repeated activation of these areas in succession lead to “consolidation” of the trace within the neocortex. Once consolidation is sufficiently complete, the memory trace becomes mediated through neocortical activity alone and the MTH is no longer necessary for re-activation.
Figure 1 provides a visual explanation of the standard model. Initially, the memory trace (features of the experience represented by red circles) is weak in the neocortex and is reliant on its connections to the medial temporal hippocampal system (MTH) for retrieval. Over time, an intrinsic process results in the strengthening of the connections between memory trace representations in the neocortex. Since the connections are consolidated, the memory can now be retrieved without the hippocampus.
While never explicitly described by Squire and colleagues, the timescale of MTH-dependence in memory formation and maintenance is believed to vary by species as well as by the extent of hippocampal damage. For example, hippocampal lesion experiments with mouse models have shown retrograde amnesia for approximately one week prior to surgery, while case studies of human subjects with similar hippocampal damage have had retrograde amnesia limited to around two to three years prior to the accident).
The standard model of systems consolidation largely applies to the formation of declarative memories, which include semantic, factual memories and episodic
Episodic
Episodic can refer to* The nature of television series that are divided into short programs. See Episode* Episodic memory relates to the types of memory that result from specific incidents in a lifetime...
, autobiographical memories. This has been supported by case studies of human patients with MTH lesions who exhibit difficulties in remembering experiences and fact learned post-surgery, however are able to retain motor and skill memories such as how to ride a bike or perform mirror tracing tasks.