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L Cahill

Publications and source records attributed to L Cahill.

At least 19 recordsLinked to original sources
PubMed2000

Event-related activation in the human amygdala associates with later memory for individual emotional experience.

The role of the amygdala in enhancing declarative memory for emotional experiences has been investigated in a number of animal, patient, and brain imaging studies. Brain imaging studies, in particular, have found a correlation between amygdala activation during encoding and subsequent memory. Because of the design of these studies, it is unknown whether this correlation is based on individual differences between participants or within-subject variations in moment-to-moment amygdala activation related to individual stimuli. In this study, participants saw neutral and negative scenes and indicated how emotionally intense they found each scene. Separate functional magnetic resonance imaging responses in the amygdala for each scene were related to the participants' report of their experience at study and to performance in an unexpected memory test 3 weeks after scanning. The amygdala had the greatest response to scenes rated as most emotionally intense. The degree of activity in the left amygdala during encoding was predictive of subsequent memory only for scenes rated as most emotionally intense. These findings support the view that amygdala activation reflects moment-to-moment subjective emotional experience and that this activation enhances memory in relation to the emotional intensity of an experience.

Amygdala↗
PubMed2000

Relative sparing of emotionally influenced memory in Alzheimer's disease.

Studies suggest that emotionally influenced events enhance long-term memory. This study aimed to uncover whether this phenomenon exists in Alzheimer's Disease (AD) by comparing patients' performance with that of controls on a memory task. Overall, controls performed better than AD subjects on a delayed recognition task of a story containing emotional elements (95.8+/-2.4% vs 66.6+/-28.5%; mean +/- s.d.), respectively. Among AD subjects, there was relative sparing of emotionally influenced memory, which was not seen in controls because of a ceiling effect. Retention of the emotional phase of the story differed significantly from that of the neutral phases. These findings suggest that the influence of emotion on memory is spared, at least to some degree, in AD.

Aged↗
PubMed2000

Impaired memory consolidation in rats produced with beta-adrenergic blockade.

Despite abundant evidence that systemic administration of adrenergic drugs and hormones can produce retrograde memory enhancement, the literature contains no clear demonstration that postlearning systemic administration of adrenergic antagonists produces retrograde amnesia. Here we demonstrate retrograde amnesia for a stressful learning task (a spatial water maze) with systemic administration of the beta-adrenergic antagonist propranolol (5 mg/kg). The amnesic effect of the drug depended on the degree of learning in the subjects: Propranolol caused a robust retrograde amnesia in "good learners," but did not significantly affect memory in "poor learners." The findings provide critical additional support for the hypothesis that postlearning adrenergic activation modulates memory consolidation processes after emotionally stressful events and help explain previous failures to detect memory impairment after systemic administration of adrenergic blocking drugs.

Adrenergic beta-Antagonists↗
PubMed2000

The basolateral amygdala complex is involved with, but is not necessary for, rapid acquisition of Pavlovian 'fear conditioning'.

A major hypothesis about lateral/basolateral amygdala complex (BLC) function in memory proposes that the BLC is the site where conditioned stimulus-unconditioned stimulus (CS-US) associations are formed and permanently stored during Pavlovian 'fear conditioning.' Thus, according to this hypothesis, the BLC is necessary for the acquisition and expression of both discrete-cue and contextual Pavlovian fear conditioning. This hypothesis clearly requires that animals with complete lesions of the BLC be completely unable to acquire Pavlovian fear conditioning. In this experiment, distribution of training and testing trials over three sessions revealed that rats with complete BLC lesions rapidly acquired a contextual CS-US association (as assessed with freezing behaviour), although their performance, as expected, did not equal that of sham operated controls. Irrespective of the nature of the freezing deficit relative to controls, the learning in the BLC-lesioned rats strongly indicates that Pavlovian fear conditioning CS-US associations can be rapidly acquired in the absence of the BLC, and that the BLC cannot therefore be necessary for their acquisition.

Amygdala↗
PubMed2000

The brain decade in debate: I. Neurobiology of learning and memory.

This article is a transcription of an electronic symposium in which some active researchers were invited by the Brazilian Society for Neuroscience and Behavior (SBNeC) to discuss the last decade's advances in neurobiology of learning and memory. The way different parts of the brain are recruited during the storage of different kinds of memory (e.g., short-term vs long-term memory, declarative vs procedural memory) and even the property of these divisions were discussed. It was pointed out that the brain does not really store memories, but stores traces of information that are later used to create memories, not always expressing a completely veridical picture of the past experienced reality. To perform this process different parts of the brain act as important nodes of the neural network that encode, store and retrieve the information that will be used to create memories. Some of the brain regions are recognizably active during the activation of short-term working memory (e.g., prefrontal cortex), or the storage of information retrieved as long-term explicit memories (e.g., hippocampus and related cortical areas) or the modulation of the storage of memories related to emotional events (e.g., amygdala). This does not mean that there is a separate neural structure completely supporting the storage of each kind of memory but means that these memories critically depend on the functioning of these neural structures. The current view is that there is no sense in talking about hippocampus-based or amygdala-based memory since this implies that there is a one-to-one correspondence. The present question to be solved is how systems interact in memory. The pertinence of attributing a critical role to cellular processes like synaptic tagging and protein kinase A activation to explain the memory storage processes at the cellular level was also discussed.

Amygdala↗
PubMed1999

The role of overt rehearsal in enhanced conscious memory for emotional events.

This study tested the hypothesis that overt rehearsal is sufficient to explain enhanced memory associated with emotion by experimentally manipulating rehearsal of emotional material. Participants viewed two sets of film clips, one set of emotional films and one set of relatively neutral films. One set of films was viewed in each of two sessions, with approximately 1 week between the sessions. Participants were given a free recall test of all of films viewed approximately 1 week after the second session. Rehearsal was manipulated by instructing one group of participants not to discuss the films with anyone (no talk group) and instructing a second group to discuss both sets of films with at least three people (forced talk group). A third group consisted of participants instructed not to discuss the films with anyone, but who did not comply with these instructions (talkers group). All groups recalled significantly more of the emotional films than the neutral films. Furthermore, the relative number of emotional and neutral films recalled did not differ significantly among the three groups. The results indicate that overt rehearsal is insufficient to explain the enhancing effects of emotion on memory.

Analysis of Variance↗
PubMed1999

Stimulation of the noradrenergic system enhances and blockade reduces memory for emotional material in man.

BACKGROUND: It is clearly established that emotional events tend to be remembered particularly vividly. The neurobiological substrates of this phenomenon are poorly understood. Recently, the noradrenergic system has been implicated in that beta blockade has been shown to reduce significantly the delayed recall of emotional material with matched neutral material being unaffected. METHODS: In the present study, 36 healthy young adults were randomly allocated to receive either yohimbine, which stimulates central noradrenergic activity, metoprolol which blocks noradrenergic activity, or matched placebo. The three groups were well matched. All capsules were taken orally, prior to viewing a narrated 11 slide show described a boy being involved in an accident. RESULTS: Yohimbine significantly elevated, and metoprolol reduced mean heart rate during the slide show relative to placebo, thus confirming the efficacy of the pharmacological manipulation. One week later, in a surprise' test, memory for the slide show was tested. As predicted, yohimbine-treated subjects recalled significantly more and metoprolol subjects fewer slides relative to placebo. This result was confirmed via analysis of multiple-choice recognition memory scores. CONCLUSIONS: We conclude that stimulation of the noradrenergic system results in the enhancement and blockade in a reduction of recall and recognition of emotional material in man.

Adrenergic alpha-Agonists↗
PubMed1999

Hemispheric lateralization in the processing of odor pleasantness versus odor names.

It is well established that for most people linguistic processing is primarily a left hemisphere activity, whereas recent evidence has shown that basic odor perception is more lateralized to the right hemisphere. Importantly, under certain conditions, emotional responding also shows right hemisphere laterality. Hedonic (pleasantness) assessments constitute basic level emotional responses. Given that olfaction is predominantly ipsilateral in function, it was hypothesized that odor pleasantness evaluations may be accentuated by right nostril perception and that odor naming would be superior with left nostril perception. To test this prediction we presented eight familiar neutral-mildly pleasant odors for subjects to sniff through the left and right nostrils. Subjects smelled each odor twice (once through each nostril) at two different sessions, separated by 1 week. At each session subjects provided pleasantness, arousal and naming responses to each odorant. Results revealed that odors were rated as more pleasant when sniffed through the right nostril and named more correctly when sniffed through the left. No effects for arousal were obtained. These findings are consistent with previously demonstrated neural laterality in the processing of olfaction, emotion and language, and suggest that a local and functional convergence may exist between olfaction and emotional processing.

Adolescent↗
PubMed1999

Memory for emotional material: a comparison of central versus peripheral beta blockade.

The connection between affect and memory is poorly understood. A possible psychopharmacological linking mechanism is the sympathetic arousal that occurs in response to threatening or emotive material. Cahill et al. (1994) reported that a single administration of 40 mg propranolol hydrochloride, a non-selective beta-adrenergic blocker, to healthy young adults significantly reduced delayed recall of emotive material, with recall of matched neutral material unaffected. This study differed importantly from the original Cahill et al. (1994) procedure in that only the emotionally arousing narrative was employed. Using the same slide presentation as Cahill et al. (1994), an experiment was carried out in order to determine whether beta-adrenergic blockade significantly reduces recall of emotive material via a central or peripheral mode of action. Thirty-six healthy young adults were recruited as subjects. Subjects were randomly allocated to three groups: (a) placebo (b) 40 mg propranolol hydrochloride (a beta blocker which readily crosses the blood brain barrier) and (c) 40 mg nadolol (a beta blocker which does not cross the blood-brain barrier). The three groups were matched for age, sex, intelligence, personality factors, and general memory functioning. Subjects viewed a series of 11 slides accompanied by a narrative, divisible into three phases. The emotionally arousing component of the narrative was introduced during phase II. Both central and peripheral beta blockade produced the expected effects on the sympathetic nervous system, as demonstrated by reliable reductions in systolic and diastolic blood pressure. In a surprise memory test 1 week later, subjects were asked to recall as much as possible of the story and slides, and also completed a forced choice recognition memory test. All three groups showed heightened recall and recognition for the central (emotive) section of the story. There was no differential effect of beta blockade (either central or peripheral) relative to placebo. Beta blockade markedly reduced systolic and diastolic blood pressure, but resulted in no significant effect on memory for both emotional and neutral material.

Adrenergic beta-Antagonists↗
PubMed1999

A neurobiological perspective on emotionally influenced, long-term memory.

Evidence pertaining to the neurobiological mechanisms by which emotional arousal influences memory is reviewed. Substantial evidence from studies of both infra-human and human subjects converges on the view that the enhancing effect of emotional arousal on long-term memory formation depends on an endogenous memory modulatory mechanism consisting of, at minimum, the adrenergic system and the amygdala. Relatively unrelated to memory formation for nonemotionally arousing events, this mechanism is thought to operate during and after an emotionally stressful event, and provide a means by which long-term memory storage is ""weighted" in general proportion to the importance of the information being stored. Potential malfunctions of this normally adaptive mechanism, and some therapeutic possibilities these potential malfunctions raise, are also discussed.

Animals↗
PubMed1998

Hippocampal, but not amygdala, activity at encoding correlates with long-term, free recall of nonemotional information.

Participation of two medial temporal lobe structures, the hippocampal region and the amygdala, in long-term declarative memory encoding was examined by using positron emission tomography of regional cerebral glucose. Positron emission tomography scanning was performed in eight healthy subjects listening passively to a repeated sequence of unrelated words. Memory for the words was assessed 24 hr later with an incidental free recall test. The percentage of words freely recalled then was correlated with glucose activity during encoding. The results revealed a striking correlation (r = 0.91, P < 0.001) between activity of the left hippocampal region (centered on the dorsal parahippocampal gyrus) and word recall. No correlation was found between activity of either the left or right amygdala and recall. The findings provide evidence for hippocampal involvement in long-term declarative memory encoding and for the view that the amygdala is not involved with declarative memory formation for nonemotional material.

Adolescent↗
PubMed1998

Memory for emotional events: differential effects of centrally versus peripherally acting beta-blocking agents.

Substantial evidence from animal research indicates that enhanced memory associated with emotional experiences involves activation of the beta-adrenergic system. This hypothesis is further supported by the finding in human subjects that blockade of beta-adrenergic receptors with propranolol selectively reduced memory for emotional events. In the present study, we compared the effects of propranolol, a lipid soluble drug which crosses the blood-brain barrier easily, with those of nadolol, a water soluble drug which crosses the blood-brain barrier to a considerably lesser extent, to determine whether the effect involved peripheral or central beta-adrenergic receptors. The effects of these drugs, taken before subjects watched a slide show that was either emotionally arousing or relatively neutral in content, were tested 1 week later with a surprise memory test. Consistent with previous results, propranolol impaired memory (recall and recognition) in the subjects who saw the emotional version of the slide show. In contrast, nadolol did not impair memory of the emotional slide show. These results indicate that the blockade of central beta-adrenergic receptors is responsible for the reduction in storage of emotional events. The results support the view that memory of a mild emotional event involves activation of central, but not necessarily peripheral beta-adrenergic receptors.

Adrenergic beta-Antagonists↗
PubMed1998

Mechanisms of emotional arousal and lasting declarative memory.

Neuroscience is witnessing growing interest in understanding brain mechanisms of memory formation for emotionally arousing events, a development closely related to renewed interest in the concept of memory consolidation. Extensive research in animals implicates stress hormones and the amygdaloid complex as key, interacting modulators of memory consolidation for emotional events. Considerable evidence suggests that the amygdala is not a site of long-term explicit or declarative memory storage, but serves to influence memory-storage processes in other brain regions, such as the hippocampus, striatum and neocortex. Human-subject studies confirm the prediction of animal work that the amygdala is involved with the formation of enhanced declarative memory for emotionally arousing events.

Amygdala↗
PubMed1997

The neurobiology of emotionally influenced memory. Implications for understanding traumatic memory.

Substantial evidence from animal and human subject studies converges on the view that memory for emotionally arousing events is modulated by an endogenous memory-modulating system consisting, at minimum, of stress hormones and the amygdaloid complex. Within the normal range of emotions experienced, this system is viewed as an evolutionarily adaptive method of creating memory strength that is, in general, proportional to memory importance. In conditions of extreme emotional stress, the operation of this normally adaptive system may underly the formation of strong, "intrusive" memories characteristic of PTSD. An improved understanding of the neurobiology of memory modulation should lead to an improved ability to treat or prevent traumatic memories.

Brain↗
PubMed1997

Interaction of neuromodulatory systems in modulating memory storage.

An implicit assumption guiding many studies of neurochemical systems involved in learning and memory in animal subjects is that animal and human memory systems use the same or similar mechanisms. Because acquisition and retention performance can be influenced by many processes other than information storage, special effort is required to distinguish influences on memory processes from other factors influencing performance. This article reviews the findings of recent studies investigating the effects, on memory, of drugs affecting adrenergic, opioid peptidergic, GABAergic and cholinergic systems. The review focuses primarily on studies using posttraining treatments and tests for retention given no sooner than a day after the training. Extensive evidence suggests that such drugs interact within the amygdaloid complex and that projections from the amygdala influence memory storage in other brain regions. The assumption that comparable processes occur in animal and human subjects is supported by evidence that, in human subjects, emotionally influenced memory is blocked by a beta-adrenergic blocker and by lesions of the amygdaloid complex.

Animals↗
PubMed1997

Emotional perception and memory in amnesia.

The authors examined whether perception of emotional stimuli is normal in amnesia and whether emotional arousal has the same enhancing effect on memory in amnesic patients as it has in healthy controls. Forty standardized color pictures were presented while participants rated each picture according to emotional intensity (arousal) and pleasantness (valence). An immediate free-recall test was given for the pictures, followed by a yes-no recognition test. Arousal and valence ratings were highly similar among the amnesic patients and controls. Emotional arousal (regardless of valence) enhanced both recall and recognition of the pictures, and this enhancement was proportional for amnesic patients and controls. Results suggest that emotional perception and the enhancing effect of emotional arousal on memory are intact in amnesia.

Aged↗