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Biomedical subjects

L Cahill

Publications and source records attributed to L Cahill.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1996

Involvement of the amygdala in memory storage: interaction with other brain systems.

There is extensive evidence that the amygdala is involved in affectively influenced memory. The central hypothesis guiding the research reviewed in this paper is that emotional arousal activates the amygdala and that such activation results in the modulation of memory storage occurring in other brain regions. Several lines of evidence support this view. First, the effects of stress-related hormones (epinephrine and glucocorticoids) are mediated by influences involving the amygdala. In rats, lesions of the amygdala and the stria terminalis block the effects of posttraining administration of epinephrine and glucocorticoids on memory. Furthermore, memory is enhanced by posttraining intraamygdala infusions of drugs that activate beta-adrenergic and glucocorticoid receptors. Additionally, infusion of beta-adrenergic blockers into the amygdala blocks the memory-modulating effects of epinephrine and glucocorticoids, as well as those of drugs affecting opiate and GABAergic systems. Second, an intact amygdala is not required for expression of retention. Inactivation of the amygdala prior to retention testing (by posttraining lesions or drug infusions) does not block retention performance. Third, findings of studies using human subjects are consistent with those of animal experiments. beta-Blockers and amygdala lesions attenuate the effects of emotional arousal on memory. Additionally, 3-week recall of emotional material is highly correlated with positronemission tomography activation (cerebral glucose metabolism) of the right amygdala during encoding. These findings provide strong evidence supporting the hypothesis that the amygdala is involved in modulating long-term memory storage.

Amygdala↗
PubMed1996

Amygdala activity at encoding correlated with long-term, free recall of emotional information.

Positron emission tomography of cerebral glucose metabolism in adult human subjects was used to investigate amygdaloid complex (AC) activity associated with the storage of long-term memory for emotionally arousing events. Subjects viewed two videos (one in each of two separate positron emission tomography sessions, separated by 3-7 days) consisting either of 12 emotionally arousing film clips ("E" film session) or of 12 relatively emotionally neutral film clips ("N" film session), and rated their emotional reaction to each film clip immediately after viewing it. Three weeks after the second session, memory for the videos was assessed in a free recall test. As expected, the subjects' average emotional reaction to the E films was higher than that for the N films. In addition, the subjects recalled significantly more E films than N films. Glucose metabolic rate of the right AC while viewing the E films was highly correlated with the number of E films recalled. AC activity was not significantly correlated with the number of N films recalled. The findings support the view derived from both animal and human investigations that the AC is selectively involved with the formation of enhanced long-term memory associated with emotionally arousing events.

Adult↗
PubMed1996

Alteration of auditory cortex activity with a visual stimulus through conditioning: a 2-deoxyglucose analysis.

In two experiments, the 2-deoxyglucose metabolic mapping technique was used to examine the hypothesis that a stimulus of one modality (a light) will begin to activate the sensory cortex of a stimulus of another modality (a tone) with which it has been repeatedly paired. Adult gerbils received repeated presentations of either a light or the light paired with a tone known to affect 2DG labeling patterns in the auditory cortex. Intermittent footshock was included on a pseudo-random basis to maintain arousal in the subjects. One day after training, each gerbil was injected with 2DG and either received repeated presentations of the light only or was simply exposed to the training context. Analysis of the auditory cortex revealed no differences in overall metabolic activity of the auditory cortex between the groups. However, in both experiments, the light that was previously paired with the tone changed the relative activity of the cortical subfields compared to the light not previously paired with the tone. Specifically, the results indicate greater activity in the anterior auditory field (AAF-Experiments 1 and 2) and the posterior fields (DPVP-Experiment 2) relative to the primary field AI in response to the light that was previously paired with the tone during training. Gerbils either only placed in the context during the 2DG session or that received unpaired presentations of the light and tone during training did not show this shift in relative labeling between the subfields. Because no differences in overall activity of the auditory cortex were found, we conclude that the shift in relative labeling between the subfields reflects, on average, both an increase in activity of fields AAF and DPVP and a concomitant decrease in AI activity in response to the light stimulus. The results have implications for our understanding both of brain learning mechanisms in general and the potential functions of auditory cortex subfields in particular.

Animals↗
PubMed1996

Modulation of memory storage.

For several decades, the concept of modulation of memory storage has significantly influenced research investigating neurobiological memory mechanisms. New evidence provides additional support for the view that stress hormones released during emotionally arousing situations modulate memory processes. Recent experiments have investigated the role of sympathetic adrenomedullary hormones in emotional memory in humans, as well as the role of adrenocortical hormones, primarily in animal studies. Further, it is becoming increasingly clear that the sympathetic adrenomedullary and the pituitary adrenocortical systems interact to modulate memory storage. Other new evidence emphasizes the role of peripheral influences to the brain on emotional memory, as well as the critical contribution of the amygdaloid complex in modulation of memory by emotional arousal.

Adrenal Cortex Hormones↗