Focal retrograde amnesia associated with vascular headache

We report the case of a 42-year-old man with repeated attacks of headache associated with retrograde amnesia. Neuropsychological tests before and after the major episode of amnesia showed mild neuropsychological deficits but with spared anterograde memory and learning functions. The amnesia was dense for a period of 15–20 years and included people and events (public and private). There was also a suggestion of amnesia for learned skills. Neurologically he had mild clinical signs and focal EEG-abnormalities in the left fronto-temporal region, but CT, MRI, and SPECT showed no abnormality. Five years after the onset of amnesia there was no recovery of the retrograde memory deficit, but a PET (glucose) scan was normal and neuropsychological testing showed no deficits. An association with migraine has been reported for some non-classical amnesias, but this is the first case of selective retrograde amnesia in a patient with headache as a primary neurological diagnosis.     

Hippocampal contributions to recollection in retrograde and anterograde amnesia

Lesions restricted to the hippocampal formation and/or extended hippocampal system (hippocampal formation, fornix, mammillary bodies, and anterior thalamic nuclei) can disrupt conscious recollection in anterograde amnesia, while leaving familiarity-based memory relatively intact. Familiarity may be supported by extra-hippocampal medial temporal lobe (MTL) structures. Within-task dissociations in recognition memory best exemplify this distinction in anterograde amnesia. The authors report for the first time comparable dissociations within recognition memory in retrograde amnesia. An amnesic patient (A.D.) with bilateral fornix and septal nuclei lesions failed to recognize details pertaining to personal past events only when recollection was required, during recognition of episodic details. His intact recognition of generic and semantic details pertaining to the same events was ascribed to intact familiarity processes. Recollective processes in the controls were reflected by asymmetrical Receiver's Operating Characteristic curves, whereas the patient's Receiver's Operating Characteristic was symmetrical, suggesting that his inferior recognition performance on episodic details was reliant on familiarity processes. Anterograde and retrograde memories were equally affected, with no temporal gradient for retrograde memories. By comparison, another amnesic person (K.C.) with extensive MTL damage (involving extra-hippocampal MTL structures in addition to hippocampal and fornix lesions) had very poor recognition and no recollection of either episodic or generic/semantic details. These data suggest that the extended hippocampal system is required to support recollection for both anterograde and retrograde memories, regardless of their age.     

Extensive temporally graded retrograde amnesia for personal-episodic facts in transient global amnesia

Abstract

Transient global amnesia (TGA) is characterized by an impairment of episodic memory resulting both in anterograde and retrograde amnesia. Few studies have assessed retrograde amnesia in TGA. Only Evans et al. (Journal of Neurology, Neurosurgery and Psychiatry 1993; 56: 1227-30) have distinguished between the episodic and semantic components of autobiographical memory, suggesting a disturbance of autobiographical incident recollection. A patient was tested during the acute phase of TGA with a sophisticated autobiographical event interview [derived from Kopelman et al. (Journal of Clinical and Experimental Neuropscyhology 1989; 11: 724-44) and Borrini et al. (Psychological Medicine 1989; 19: 215-24)], designed to replicate and extend this study of autobiographical memory. The autobiographical event interview disclosed an extensive disturbance in recalling memories with a temporal gradient, sparing earliest memories compared to more recent ones.     

Two cases of functional focal retrograde amnesia with impairment of object use

We report on two patients, TH and KN, with focal retrograde amnesia (FRA). Their memory loss regarding life events extended to their whole lives, whereas they could acquire and retain new information. They also showed prominent deficits in production and comprehension of common words. In addition, at least in the testing situation, they were impaired in their recognition and use of familiar objects. Although both cases of FRA followed an episode that can cause brain pathology, MRI revealed no structural abnormality in either patient. Stressful situations preceding the onset were evident in KN, but not in TH. We discuss their impairments of object knowledge from a neuropsychological perspective, and we interpret the etiology of their condition as a functional rather than a psychogenic amnesia.     

Pure retrograde amnesia following a mild head trauma: a neuropsychological and metabolic study

After a minor closed head injury, a 33-year-old man acquired extensive retrograde amnesia (RA) covering the previous ten years and concerning autobiographical, semantic and procedural memories. The patient's learning abilities remained excellent and he recovered considerable information from his wife, the media and personal documents. This relearned information did not, however, provide a sense of personal experience in the first weeks. CT and MRI failed to show brain damage, but EEG and SPECT examination showed a marked right temporal dysfunction. After three months the patient had almost completely recovered from RA. Interestingly, a parallel recovery was observed in the second SPECT obtained at this period. There was clearly a blockade of retrieval, while the stored engrams were probably intact. The mechanisms underlying such a functional amnesia are discussed in the light of previous reports of amnesia without brain lesions.     

Disproportionate retrograde amnesia in a patient with herpes simplex encephalitis

We describe a patient who developed a severe but temporally limited retrograde amnesia coupled with a relatively mild anterograde amnesia following herpes simplex encephalitis. The patient showed a profound retrograde amnesia for autobiographical events extending for about 10 years prior to the disease onset. Her knowledge about public events and famous persons was also impaired for this period. An MRI and SPECT demonstrated bilateral medial temporal pathology. This case represents a further instance of a relatively focal retrograde amnesia following brain damage. We review other reported cases with focal retrograde amnesia and consider theoretical and neuroanatomical accounts for the present case. Two factors may account for her amnesic patterns: a partial disruption of the store for premorbid binding codes (i.e., information that multimodal feature representations occurred synchronously); along with a relative preservation of the encoding process required to develop new synchronous codes.     

A case of persistent retrograde amnesia following a dissociative fugue: neuropsychological and neurofunctional underpinnings of loss of autobiographical memory and self-awareness

Autobiographical memory relies on complex interactions between episodic memory contents, associated emotions and a sense of self-continuity over the course of one's life. This paper reports a study based upon the case of the patient NN who suffered from a complete loss of autobiographical memory and awareness of identity subsequent to a dissociative fugue. Neuropsychological, behavioral, and functional neuroimaging tests converged on the conclusion that NN suffered from a selective retrograde amnesia following an episode of dissociative fugue, during which he had lost explicit knowledge and vivid memory of his personal past. NN's loss of self-related memories was mirrored in neurobiological changes after the fugue whereas his semantic memory remained intact. Although NN still claimed to suffer from a stable loss of autobiographical, self-relevant memories 1 year after the fugue state, a proportionate improvement in underlying fronto-temporal neuronal networks was evident at this point in time. In spite of this improvement in neuronal activation, his anterograde visual memory had been decreased. It is posited that our data provide evidence for the important role of visual processing in autobiographical memory as well as for the efficiency of protective control mechanisms that constitute functional retrograde amnesia.     

Hippocampal lesions produce both nongraded and temporally graded retrograde amnesia in the same rat

Rats were administered contextual fear conditioning and trained on a water‐maze, spatial memory task 28 days or 24 h before undergoing hippocampal lesion or control surgery. When tested postoperatively on both tasks, rats with hippocampal lesions exhibited retrograde amnesia for spatial memory at both delays but temporally graded retrograde amnesia for the contextual fear response. In demonstrating both types of retrograde amnesia in the same animals, the results parallel similar observations in human amnesics with hippocampal damage and provide compelling evidence that the nature of the task and the type of information being accessed are crucial factors in determining the pattern of retrograde memory loss associated with hippocampal damage. The results are interpreted as consistent with our transformation hypothesis (Winocur et al. (2010a) Neuropsychologia 48:2339–2356; Winocur and Moscovitch (2011) J Int Neuropsychol Soc 17:766–780) and at variance with standard consolidation theory and other theoretical models of memory. © 2013 Wiley Periodicals, Inc.     

Malingering and retrograde amnesia: the historic case of the Collegno amnesic

Assessment of feigned cognitive disorders is an important field of neuropsychology because of its applications to forensic settings. Strategies for detecting malingering in amnesia are available for anterograde amnesia. Less attention has been given to malingering in retrograde amnesia. The case of the 'Smemorato di Collegno' (The Collegno Amnesic) is probably the most famous case of malingered retrograde amnesia ever known in Italy. In 1926, a man who appeared to have lost all his autobiographical memories and identity spent nearly a year in the Collegno asylum of Turin without a name. He was later initially identified as Giulio Canella, Director of the 'Scuola Normale di Verona' who had disappeared during the war in 1916. He was suspected of later identified as being Mario Bruneri, a petty crook from Turin who played the part of an amnesic whose retrograde memory gradually returned. A lengthy investigation was required before this conclusion was reached. Several clinicians and renowned academics evaluated the case, but only Alfredo Coppola, diagnosed "malingered retrograde amnesia" using a method that was extremely innovative for the times. The aim of the present paper is to review the original cognitive evaluation and the strategies used for malingering detection in the "Collegno case". The outcome of the case is then discussed in the light of present-day forensic neuropsychology and the level of advancement of mental examination achieved in the 1920s in Europe is highlighted.     

Retrograde episodic memory and emotion: A perspective from patients with dissociative amnesia

With his recent definition of episodic memory Tulving [Tulving, E. (2005). Episodic memory and autonoesis: Uniquely human? In H. Terrace & J. Metcalfe (Eds.), The missing link in cognition: Evolution of self-knowing consciousness (pp. 3-56). New York: Oxford University Press] claims that this memory system is uniquely human and thereby distinguishes human beings from other, even highly developed, mammals. First we will define the term episodic memory as it is currently used in neuropsychological research by specifying the three underlying concepts of subjective time, autonoëtic consciousness, and the self. By doing so, we will strongly focus on retrograde episodic memory and its relation to emotion and self-referential processing. We support this relation with a discussion of autobiographical memory functions in psychiatric disorders such as dissociative amnesia. To illustrate the connection of emotion and retrograde episodic memory we shortly present neuropsychological data of two cases of dissociative amnesia. Both cases serve to point to the protective mechanism of a block of self-endangering memories from the episodic memory system, often described as the mnestic block syndrome. On the basis of these cases and supportive results from further cases we will conclude by pointing out similarities and differences of patients with organic and dissociative (psychogenic) amnesia.     

Retrograde amnesia for spatial information: a dissociation between intra and extramaze cues following hippocampus lesions in rats

Several recent studies have shown a flat retrograde amnesia for spatial information following lesions to the hippocampus in rats and mice. However, the results of the present investigation demonstrate that in rats that presurgically learned a spatial reference memory task based on extramaze cues, a temporally graded retrograde amnesia is evident following lesions to the hippocampus (1, 16, 32 or 64 days after learning) if two conditions are met. First, that a wide range of retention intervals is used, and second, that independent groups of rats are tested, not a single group that learns different spatial discrimination tasks at different times (expt 1). The results of expt 2 show that the hippocampus does not serve as a consolidating mechanism when the spatial task learned presurgically is based on intramaze cues. Taken together, these results indicate that the hippocampus is critical for the storage and/or retrieval of spatial reference information that was learned up to 1 month before hippocampus damage; however, in the absence of the hippocampus, efficient retention can still occur provided that the spatial knowledge was learned in a simple associative manner.     

Hypo-retrieval and hyper-suppression mechanisms in functional amnesia

Functional amnesia (FA) is characterized by an extensive retrograde memory loss in the absence of detectable structural brain damage. The two main hypotheses put forward to explain this disturbance involve a global retrieval deficit (affecting both pre- and post-onset memories) and a selective inability to explicitly retrieve pre-onset memories.Here, we extensively examined P.P., a patient with FA, with a view to obtaining additional insights into the cognitive and neural mechanisms underlying this disorder. In Experiments 1 and 2, post-onset memories were assessed using tasks focusing on the state of consciousness associated with their retrieval. Although subtle deficits in the ability to recollect post-onset personal events were detected, P.P.’s performances were normal when the encoding of the event was monitored in a laboratory setting. In Experiment 3, implicit recognition of pre-onset memories was tested using skin conductance responses. Results showed that P.P. responded implicitly to photographs of personal pre-onset events that were not explicitly recognized. In Experiment 4, designed to assess the patient's ability to suppress newly acquired information, P.P. suppressed more items than controls. Additionally, while no grey matter loss was evidenced with voxel-based morphometry, magnetic resonance spectroscopy and magnetization transfer imaging showed significant metabolic and structural changes within the white matter of the right prefrontal lobe.In conclusion, our results suggest that FA may result from a combination between two processes, a “hypo-retrieval” of pre-onset memories, tentatively due to white matter tract damage, and a “hyper-suppression” mechanism, concomitantly preventing the retrieval of pre-onset memories.     

Functional brain imaging in 14 patients with dissociative amnesia reveals right inferolateral prefrontal hypometabolism

Dissociative amnesia is a condition usually characterized by severely impaired retrograde memory functioning in the absence of structural brain damage. Recent case studies nevertheless found functional brain changes in patients suffering from autobiographical–episodic memory loss in the cause of dissociative amnesia. Functional changes were demonstrated in both resting state and memory retrieval conditions. In addition, some but not all cases also showed other neuropsychological impairments beyond retrograde memory deficits. However, there is no group study available that examined potential functional brain abnormalities and accompanying neuropsychological deteriorations in larger samples of patients with dissociative retrograde amnesia. We report functional imaging and neuropsychological data acquired in 14 patients with dissociative amnesia following stressful or traumatic events. All patients suffered from autobiographical memory loss. In addition, approximately half of the patients had deficits in anterograde memory and executive functioning. Accompanying functional brain changes were measured by [¹⁸F]fluorodeoxyglucose positron emission tomography (FDG-PET). Regional glucose utilization of the patients was compared with that of 19 healthy subjects, matched for age and gender. We found significantly decreased glucose utilization in the right inferolateral prefrontal cortex in the patients. Hypometabolism in this brain region, known to be involved in retrieval of autobiographical memories and self-referential processing, may be a functional brain correlate of dissociative amnesia.     

Autobiographical memory and the self in a case of transient epileptic amnesia

Transient epileptic amnesia (TEA) is characterized by deficits in autobiographical memory (AM). One of the functions of AM is to maintain the self, suggesting that the self may undergo changes as a result of memory loss in temporal lobe epilepsy. To examine this, we used a modification of a task used to assess the relationship between self and memory (the IAM task) in a single case, E.B. Despite complaints of AM loss, E.B. had no difficulty in producing a range of self-images (e.g., I am a husband) and collections of self-defining AMs in support of these statements. E.B. produced fewer episodic memories at times of self-formation, but this did not seem to impact on the maintenance of self. The results support recent work suggesting the self may be maintained in the absence of episodic memory. The application of tasks such as that used here will further elucidate AM impairment in temporal lobe epilepsy.     

Intracerebroventricular administration of nanogram amounts of beta-endorphin and Met-enkephalin causes retrograde amnesia in rats

The intracerebroventricular (icv) administration of 5.0 or 25.0 ng of beta-endorphin or Met-enkephalin causes retrograde amnesia for a shuttle avoidance task ion rats. In both cases, the higher dose was more effective than the lower one. The present results confirm previous similar findings obtained using systemic administrations of these compounds, and suggest that the amnestic effect of beta-endorphin and Met-enkephalin is mediated centrally.     

Dissociable anterograde amnesic effects of retrosplenial cortex and hippocampal lesions on spontaneous object recognition memory in rats

The amnesic effects of excitotoxic lesions of the rat retrosplenial cortex (RS) and hippocampus (HPC) in the spontaneous object recognition (SOR) performance were investigated. The SOR test consisted of the sample‐exposure session(s) and a test session. First, to test retrograde amnesia, rats received four sample‐exposure sessions within a day at 4 weeks and 1 day before the surgery, respectively. In the test sessions conducted 1 week after the surgery, both lesion groups showed a temporally ungraded retrograde amnesia. Second, to test anterograde amnesia, 1‐ and 4‐week retention intervals were inserted between the four sample‐exposure sessions and the test session. The RS‐lesioned rats showed a retention interval‐dependent impairment in the test sessions, while the HPC‐lesioned rats showed an impairment regardless of the retention interval. Finally, to test short‐term recognition memory, 5‐ or 30‐min delay was interposed between the single sample‐exposure session and the test session. Both lesion groups performed normally irrespective of the delay length. These results suggest that both the RS and HPC are important for long‐term object recognition memory, but these areas have different roles in it. © 2012 Wiley Periodicals, Inc.     

Selective lesions of basal forebrain cholinergic neurons produce anterograde and retrograde deficits in a social transmission of food preference task in rats

We examined the performance of Long-Evans rats with 192 IgG-saporin lesions of the medial septum/vertical limb of the diagonal band (MS/VDB) or nucleus basalis magnocellularis/substantia innominata (NBM/SI), which removed cholinergic projections mainly to hippocampus or neocortex, respectively. We studied the effects of these lesions on anterograde and retrograde memory for a natural form of hippocampal-dependent associative memory, the social transmission of food preference. In a study of anterograde memory, MS/VDB lesions did not affect the immediate, 24-h or 3-week retention of the task. In contrast, NBM/SI lesions severely impaired immediate and 24-h retention. In a study of retrograde memory in which rats acquired the food preference 5 days or 1 day before surgery and they were tested 10-11 days after surgery, MS/VDB-lesioned rats showed striking memory deficits for the preference acquired at a long delay (5 days) before surgery, although all lesioned rats exhibited poorer retention on both retest sessions than on their pretest performance. Subsequent testing of new anterograde learning in these rats revealed no disrupting effects of lesions on a standard two-choice test. When rats were administered a three-choice test, in which the target food was presented along with two more options, NBM/SI-lesioned rats were somewhat impaired on a 24-h retention test. These results provide evidence that NBM/SI and MS/VDB cholinergic neurons are differentially involved in a social memory task that uses olfactory cues, suggesting a role for these neurons in acquisition and consolidation/retrieval of nonspatial declarative memory.     

Retrograde and anterograde object recognition in rats with hippocampal lesions

Retrograde and anterograde object-recognition memory was assessed in rats with cytotoxic lesions of the hippocampal formation (HPC), using a paradigm based on the natural tendency of rats to spend more time exploring novel objects than familiar objects. The rats were allowed to explore a sample object for 5 min/day on 5 consecutive days, either 5 weeks or 1 week before surgery. After surgery, retrograde recognition was assessed by comparing the amount of time spent exploring the sample versus a novel object in a free-choice situation. Control rats spent more time exploring the novel object than the sample objects from both presurgery time periods, whereas rats with HPC lesions did not discriminate between the novel objects and sample objects from either presurgery time period. Despite their deficits on the retrograde recognition test, the rats with HPC lesions performed like control rats on anterograde recognition tests, displaying a strong exploratory preference for novel objects over sample objects, with retention delays of either 15 min or 24 h. The findings suggest that extrahippocampal circuitry is capable of supporting object recognition, but only if the HPC does not participate in encoding the original encounter with the object.     

Anterograde and retrograde amnesia in a person with bilateral fornix lesions following removal of a colloid cyst

AD, a 45-year-old man, presented with a severe and global anterograde amnesia following surgery for removal of a colloid cyst. Structural neuroimaging confirmed bilateral lesions to the fornix and a small lesion in the basal forebrain. Testing for remote episodic memory of autobiographical events, and for remote semantic memory of personal and public events, and of famous people, revealed that AD had a severe retrograde amnesia for autobiographical episodes that covered his entire lifetime, and a time-limited retrograde amnesia for semantic memory. Because the fornix and basal forebrain lesions disrupted major afferent and efferent pathways of the hippocampus, it was concluded that the integrity of the hippocampus and its projections are needed to retain and/or recover autobiographical memories no matter how old they are. By contrast, hippocampal contribution to semantic memory is time-limited. These findings were interpreted as consistent with Multiple Trace Theory, which holds that the hippocampal system is essential for recovering contextually rich memories no matter how old they are, but is not needed for recovering semantic memories.