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PubMed2000

Evolution of temporal lobe hypoperfusion in transient global amnesia: a serial single photon emission computed tomography study.

Previous functional neuroimaging studies performed during transient global amnesia (TGA) have not answered the central question regarding the etiology of TGA, namely: whether the observed hypoperfusion in the mesial temporal lobe structures reflects a primarily ischemic process or whether it represents a secondary phenomenon resulting from locally decreased metabolism. The authors performed Tc 99-m-bicisate brain single photon-emission computed tomography (SPECT) scanning in a 66-year-old man during an episode of TGA, 24 hours after the episode and 3 months after the episode. To the authors' knowledge, this is the only reported study in which a follow-up SPECT scan was performed within 24 hours. The initial study showed bilateral mesial temporal lobe hypoperfusion that partially resolved after 24 hours and returned to normal at 3 months. Resolution of the SPECT scan abnormalities correlated well with resolution of the memory loss. These findings agree with previously reported SPECT, positron-emission tomography (PET), and diffusion magnetic resonance imaging (MRI) studies that indicate the mesial temporal lobe structures as the major site of pathology in TGA. The authors suggest that a process causing decreased local metabolism, such as cortical spreading depression, constitutes the primary pathophysiologic mechanism in this case.

Aged↗
PubMed1965

A brief temporal gradient of retrograde amnesia independent of situational change.

Rats were given a single electroconvulsive shock at varying intervals after receiving a punishing shock to the feet immediately after stepping into a compartment. Significant amounts of retrograde amnesia for the memory of the punishment was shown when electroconvulsive shock was administered up to and including 30 seconds after the punishment but not at 60 seconds. This brief temporal gradient cannot be explained in ternis of changed stimulus cues or learned interference analogouS to retroactive inhibition.

Amnesia↗
PubMed1966

Amnesia or reversal of forgetting by anticholinesterase, depending simply on time of injection.

The effect of intracerebral injections of the anticholinesterase drug diisopropyl fluorophosphate in rats was to produce good recall of an otherwise almost forgotten habit learned 28 days before. The same injections produced temporary amnesia for the same habit, otherwise well remembered, learned 14 days before. The injections had no ef fect on the memory of the same habit when it was only partly learned 14 days before. The results support the hy pothesis that the physiological basis of memory lies in an increase, and for getting in a decrease, in synaptic con ductance.

Amnesia↗
PubMed1967

Recovery of memory after amnesia induced by electroconvulsive shock.

Electroconvulsive shock given to rats immediately after one-trial avoidance learning produced a significant amnesic effect 24 hours later; this amnesia had largely disappeared in further retention tests 48 and 72 hours after treatment. This result puts in question a basic assumption implicit in most memory consolidation studies that such amnesic effects will be permanent.

Amnesia↗
PubMed1968

Retrograde amnesia produced by electroconvulsive shock after reactivation of a consolidated memory trace.

Rats had a memory loss of a fear response when they received an electroconvulsive shock 24 hours after the fear-conditioning trial and preceded by a brief presentation of the conditioned stimulus. No such loss occurred when the conditioned stimulus was not presented. The memory loss in animals given electroconvulsive shock 24 hours after conditioning was, furthermore, as great as that displayed in animals given electroconvulsive shock immediately after conditioning. This result throws doubt on the assertion that electroconvulsive shock exerts a selective amnesic effect on recently acquired memories and thus that electroconvulsive shock produces amnesia solely through interference with memory trace consolidation.

Amnesia↗
PubMed1973

Retrograde amnesia and the "reminder effect": an alternative interpretation.

Recent findings suggest that amnesic agents block the retrieval of stored information. "Reminder" treatments, such as noncontingent punishments given after the production of amnesia for avoidance learning, improve the later retention performance of an animal. The data reported suggest that noncontingent treatments provide an additional learning experience which adds to the retention performance of partially amnesic or poorly trained animals.

Amnesia↗
PubMed1974

Recovery from retrograde amnesia: a learning process.

Retrograde amnesia was produced in rats by electroconvulsive shock. Memory recovered if the animals were given repeated test trials. Memory did not recover if steps were taken to reduce the conditioning properties of the test trials; the manipulations included eliminating the response, altering the apparatus cues, or extinguishing conditioned "fear" by confining animals to the apparatus during the first test trial.

Amnesia↗
PubMed2000

Neuroscience. Video game images persist despite amnesia.

On page 350, researchers report the results of new work in which they used the computer game Tetris--which involves using spatial reasoning to slot falling blocks strategically into place--to study how the brain reviews what it has learned. The researchers found that people who have just learned to play Tetris have vivid images of the game pieces floating before their eyes as they fall asleep, a phenomenon the researchers say is critical for building memories. Much more surprisingly, the team also found that the images appear to people with amnesia who have played the game--even though they have no recollection of having done so.

Amnesia↗
PubMed1982

The neuroanatomy of amnesia: amygdala-hippocampus versus temporal stem.

Using a task known to be sensitive to human amnesia, we have evaluated two current hypotheses about which brain regions must be damaged to produce the disorder. Monkeys with bilateral transections of the white matter of the temporal stem were unimpaired, but monkeys with conjoint amygdala-hippocampal lesions exhibited a severe memory deficit. The results indicate that the hippocampus, amygdala, or both, but not the temporal stem, are involved in memory in the monkey and suggest that a rapprochement between the findings for the human and the nonhuman primate may be close at hand.

Amnesia↗
PubMed2006

The significance of post-traumatic amnesia as a risk factor in the development of olfactory dysfunction following head injury.

OBJECTIVE: To test the following hypothesis in the assessment of head injury PATIENTS: only patients with 5 min or more of post-traumatic amnesia (PTA) are at risk of acute olfactory dysfunction (OD). METHODS: This was a retrospective comparative study of olfactory status in head injury patients seen at a head injury clinic at Glasgow Royal Infirmary from 1985 to 2003. Of 828 clinic attenders, 101 had acute OD. These subjects were compared with a randomly selected control group of 102 patients with head injury but normal olfactory function. The main outcome measure was a significant likelihood of patients with PTA lasting for 5 or more minutes having acute OD compared with those with PTA of less than 5 min. RESULTS: The likelihood of patients with a PTA of 5 min or more having acute OD compared to those with PTA of less than 5 min is clinically significant with an odds ratio of 9.6 (p<0.01). CONCLUSION: Examination of patients with 5 min or more of PTA should include a simple test of sense of smell. Patients with impaired smell sensation should be aware of their condition prior to discharge from hospital. In addition, the need for a CT brain scan and appropriate follow up should be considered.

Acute Disease↗
PubMed2005

DWI in transient global amnesia and TIA: proposal for an ischaemic origin of TGA.

There are conflicting reports concerning signal intensity changes in transient global amnesia (TGA) using diffusion weighted imaging (DWI). We prospectively analysed DWI signal intensity changes in TIA and TGA patients, and compared the clinical characteristics and risk factors of both groups. Using DWI and conventional T1 and T2 weighted turbo spin echo sequences, 28 patients with acute TGA (13 men, mean age 61.5 years) and 74 TIA patients (47 men, mean age 62.4 years) were studied within 48 hours after symptom onset. Every patient underwent an intensive diagnostic investigation. In 10/28 (36%) of the TGA patients and 21/74 (28%) of the TIA patients, DWI signal intensity changes occurred. The time to DWI and the duration of symptoms were comparable in TIA and TGA patients. Overall, TIA patients showed an increased prevalence of vascular risk factors compared with TGA patients. In the TGA group, patients with abnormal DWI showed carotid atherosclerosis significantly more frequently. Based on our data, we suggest that the aetiology of TGA could be explained by an ischaemic event; due to arterial thrombembolic ischaemia in one subgroup, particularly in those patients with increased vascular risk factors, and due to venous ischaemia in another subgroup with valsalva-like activities before symptom onset.

Amnesia↗
PubMed2005

Internal jugular vein valve incompetence and intracranial venous anatomy in transient global amnesia.

BACKGROUND: Recently a causal relation between internal jugular vein valve incompetence (IJVVI) and transient global amnesia (TGA) has been suggested. IJVVI is postulated to provoke a transient mesiotemporal ischaemia by venous congestion. This mechanism requires a patent venous pathway from the affected IJV through the transverse sinus, confluens, straight sinus (SS), vein of Galen into the basal vein of Rosenthal and the internal cerebral veins. OBJECTIVE: To study IJVVI in TGA patients in relation to the intracranial venous anatomy. METHODS: IJVVI was defined if a repeated Valsalva manoeuvre (VM) led to a retrograde jugular flow detected by extracranial duplex ultrasound. Non-contrast venous MR angiography (MRA) was performed to analyse intracranial drainage patterns of the SS in relation to the side of the IJVVI. SS drainage was differentiated into three groups: predominantly right, left, and bilateral drainage. Ultrasound studies were performed in 25 TGA patients and 85 age matched controls. Twenty patients underwent venous MRA. RESULTS: Sixty eight per cent of patients and 33% of controls showed unilateral or bilateral IJVVI (p = 0.0025). In 36% of patients a TGA preceding VM was reported. Drainage pattern of SS and side of IJVVI corresponded in five of eight patients (63%) with VM and four of 12 patients without VM (33%, p = 0.0994). CONCLUSION: Our study confirms the significantly higher prevalence of IJVVI in TGA patients. However, no specific IJVVI related intracranial venous drainage patterns could be found to further support the hypothesis of a direct causal relation between IJVVI and TGA.

Adult↗
PubMed1975

Cognitive recovery after severe head injury. 2. Wechsler Adult Intelligence Scale during post-traumatic amnesia.

The Wechsler Adult Intelligence Scale (WAIS) was administered to two matched groups of severely head-injured patients. The first administration was early in the recovery period, when group I was still in post-traumatic amnesia. The WaiS results for this group were significantly lower than those of group II, who were fully conscious. A follow-up at a later stage of recovery found that group I had substantially caught up with group II on the WAIS. At both administrations the WAIS subtest scores were correlated with clinical data, and changes in the pattern of correlations between PTA and full consciousness suggested that the former represents a qualitatively, and not merely quantitatively, distinct phase of recovery.

Adult↗
PubMed1976

Cognitive recovery after severe head injury. 3. WAIS verbal and performance IQs as a function of post-traumatic amnesia duration and time from injury.

Two studies are reported are reported in which severely head-injured patients were followed up and Verbal (VIQ) and Performance (PIQ) IQs obtained on the Wechsler Adult Intelligence Scale at four intervals after injury. In the first study 51 patients were systematically followed, and results were based upon serial testing. In the second study results were based on the earliest data available from an additional 98 patients who had not been followed so systematically, in order to introduce a control for the effects of practice. Patients in both studies were categorised into four groups of the severity of head injury based upon duration of post-traumatic amnesia (PTA). In both studies, VIQ level was found to be related to PTA duration at three months after injury, while PIQ was related to PTA duration at both three and six months. No such relationships were found at 12 and 30 months after injury. Results are discussed in the context of previous studies relating the outcome of head injury to the duration of PTA.

Adult↗
PubMed1976

Diencephalic amnesia: a reappraisal.

The anatomical basis of memory disorder related to lesions of the diencephalon is a controversial matter. A study of a patient who developed severe amnesia in association with bilateral metastatic tumour invasion of the medial and posterior thalamus is reported. The findings in this case have led to further discussion of this unsettled issue.

Amnesia↗
PubMed1980

Transient global amnesia--a hippocampal phenomenon?

A case of transient global amnesia of clear vascular aetiology is described. Results of neuropsychological testing carried out during the attack clarify the nature of the memory disorder and suggest that the critical region of ischaemia is the medial temporal area around the hippocampus. Follow-up testing suggests that no lasting memory impairment resulted.

Adult↗
PubMed1982

Colour association and "colour amnesia" in aphasia.

"Colour association" performance of 50 aphasic patients was investigated by means of a test in which they identified the characteristic colours of objects shown in line drawings. All aphasics with defects in colour association were impaired in reading comprehension. However, some (33%) retained normal aural comprehension. Approximately half the aphasics with receptive language impairment performed normally in colour association. The findings suggest that "colour amnesia" may be the result of a specific cognitive disturbance which is also responsible for a subtype of aphasic alexia.

Adult↗
PubMed1988

Learning and forgetting during posttraumatic amnesia in head injured patients.

To investigate forgetting during recovery from head injury, colour slides were initially projected for long durations to ensure acquisition on a recognition test given 10 minutes later. Patients tested during posttraumatic amnesia (PTA) exhibited accelerated forgetting over 32 hours as compared with head trauma patients studied after the period of PTA and normal controls.

Adult↗