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Biomedical subjects

Larry Cahill

Publications and source records attributed to Larry Cahill.

At least 19 recordsLinked to original sources
PubMed2006

Why sex matters for neuroscience.

A rapidly burgeoning literature documents copious sex influences on brain anatomy, chemistry and function. This article highlights some of the more intriguing recent discoveries and their implications. Consideration of the effects of sex can help to explain seemingly contradictory findings. Research into sex influences is mandatory to fully understand a host of brain disorders with sex differences in their incidence and/or nature. The striking quantity and diversity of sex-related influences on brain function indicate that the still widespread assumption that sex influences are negligible cannot be justified, and probably retards progress in our field.

Animals↗
PubMed2006

A case of unusual autobiographical remembering.

This report describes AJ, a woman whose remembering dominates her life. Her memory is "nonstop, uncontrollable, and automatic." AJ spends an excessive amount of time recalling her personal past with considerable accuracy and reliability. If given a date, she can tell you what she was doing and what day of the week it fell on. She differs from other cases of superior memory who use practiced mnemonics to remember vast amounts of personally irrelevant information. We propose the name hyperthymestic syndrome, from the Greek word thymesis meaning remembering, and that AJ is the first reported case.

Adult↗
PubMed2006

Glucocorticoid release and memory consolidation in men and women.

Glucocorticoid hormones have been shown to enhance memory consolidation when applied at low doses posttraining, but are ineffective or impair memory at high doses. In a test of whether this quadratic relationship also exists for endogenously released glucocorticoids, healthy men and women received cold-pressor stress (CPS) or a control procedure immediately after reading a relatively neutral story and were tested for retention 1 week later. Cortisol levels in response to the stressor were assayed from saliva. CPS significantly elevated salivary cortisol in both sexes, but enhanced memory only in male subjects. Among CPS-treated male subjects, there was a significant quadratic correlation between cortisol release posttraining and subsequent memory. Thus, these findings represent the first demonstration of an inverted-U relationship between activity of endogenous stress hormones and human memory.

Adolescent↗
PubMed2005

His brain, her brain.

It turns out that male and female brains differ quite a bit in architecture and activity. Research into these variations could lead to sex-specific treatments for disorders such as depression and schizophrenia

Amygdala↗
PubMed2004

The influence of sex versus sex-related traits on long-term memory for gist and detail from an emotional story.

Recent findings demonstrate sex-related differences in the neurobiological mechanisms by which emotional arousal influences memory, and raise questions about the extent to which memory for emotional events may differ between males and females. Here we examine whether sex-related differences exist in the recall of central (gist) information and peripheral detail from an emotional story. Healthy subjects viewed a brief, narrated slide-show containing emotional elements in its middle section. One week later, they received an incidental multiple-choice recognition test for the story. Following the test, each subject completed the BEM Sex-Role Inventory, an assessment of sex-related masculine and feminine traits. The results reveal no differences in recall of either central or peripheral story information when considering the performance of actual men and women, but a significant difference when considering male and females as determined by their BEM test scores. "BEM" males (subjects with net male BEM scores) showed significantly enhanced recall of central emotional information. "BEM" females did not. Both groups showed significantly enhanced recall of peripheral emotional information, although this effect appeared larger in BEM females than in BEM males. The influences of "BEM" sex and type of information (central, peripheral) significantly interacted to influence emotional memory performance. These findings confirm the existence of sex-related influences in the recall of emotional information, and suggest that sex-related traits, rather than actual sex per se, may be a more sensitive indicator of these influences.

Adult↗
PubMed2003

Amygdala modulation of parahippocampal and frontal regions during emotionally influenced memory storage.

Considerable evidence from both animal and human subject research supports the hypothesis that the amygdala, when activated by emotional arousal, modulates memory storage processes in other brain regions. By this hypothesis, changes in the functional interactions of the amygdala with other brain regions during emotional conditions should underlie, at least in part, enhanced memory for emotional material. Here we examined the influence of the human amygdala on other brain regions under emotional and nonemotional learning conditions using structural equation modeling (SEqM). Eleven male subjects received two PET scans for regional cerebral glucose metabolism-one scan while viewing a series of emotionally provocative (negative) film clips and a second scan while viewing a series of more emotionally neutral film clips. Enhanced activity in the right amygdala was related to enhanced memory for the emotional films. To identify potential candidate voxels for SEqM, the functional connectivity of the maximally activated voxel within the right amygdala was investigated using partial least squares. A subset of regions identified by this analysis showing differences functional connectivity with the amygdala between the emotional versus neutral film conditions were then submitted to SEqM, which revealed significantly increased amygdala influences on the ipsilateral parahippocampal gyrus and ventrolateral prefrontal cortex during the emotional relative to the neutral film viewing condition. These findings support the view that increased influences from the amygdala, presumably reflecting its memory-modulation function, occur during emotionally arousing learning situations.

Adult↗
PubMed2003

Sex- and hemisphere-related influences on the neurobiology of emotionally influenced memory.

Recent findings are beginning to reveal apparently pronounced influences of both sex and cerebral hemisphere on the neurobiology of emotionally influenced memory. In this article, I first provide a brief, general overview of sex-related influences on brain and cognition. I next describe recent findings from my laboratory and others demonstrating sex-related influences on neural mechanisms underlying emotionally influenced explicit recall of emotionally arousing events. Both the hemispheric involvement of the human amygdala in memory for emotionally arousing events and the impairing effect of beta-adrenergic blockade on memory for emotional events, exhibit sex-related differences. I hypothesize that both of these effects relate to a modulatory influence of each amygdala on ipsilateral hemispheric function. Specifically, I hypothesize that the right hemisphere amygdala modulates right hemispheric processing of global/central aspects of a situation (an effect more pronounced in males), while the left hemisphere amygdala modulates left hemispheric processing of more local/fine detail aspects of a situation (an effect more pronounced in females). More generally, these findings presented here suggest that the interacting influences of sex and cerebral hemisphere on emotionally influenced memory are more pronounced than has been widely appreciated to date.

Animals↗
PubMed2003

Sex-related impairment of memory for emotional events with beta-adrenergic blockade.

On the basis of recent evidence indicating a sex-related lateralization of amygdala function in memory for emotional events, together with substantial evidence suggesting hemispheric specialization in processing global (central) versus local (detail) aspects of a situation, and the established dependence of the amygdala's memory modulating function on beta-adrenergic receptor activation, we predicted differential effects of a beta-adrenergic receptor antagonist (propranolol) on long-term memory for an emotionally arousing story in men and women. Specifically, we predicted that, relative to placebo, propranolol would impair memory for information central to the story line, but not memory for peripheral story details in men. Conversely, propranolol would impair memory for peripheral details, but not for central information in women. Here we confirm this prediction with a novel analysis of data from our two published studies of propranolol's effect on memory for an emotionally arousing story. These findings demonstrate a sex-related impairment of memory for emotional information by beta-adrenergic blockade. Additionally, they provide support for the hypothesis that, in this paradigm, emotional arousal enhances long-term memory for central information in men via activation of right amygdala/hemisphere function, and enhances long-term memory for peripheral details in women via activation of left amygdala/hemisphere function.

Adrenergic beta-Antagonists↗
PubMed2003

Differential effects of emotional arousal in short- and long-term memory in healthy adults.

Recent studies demonstrated important differences between short- and long-term memory mechanisms. Besides, the emotional component has a crucial role in memory formation. This study was carried out to answer whether there is a differential influence of emotional arousal in short- and long-term memory in healthy adults. Thirty-one healthy volunteers were divided into two major groups. In the first group long-term memory (LTM) was evaluated, with the testing session one week after training. The second group was tested 1h after training, where short-term memory (STM) was evaluated. Each group was divided in to two subgroups. One half of the volunteers was exposed to an emotionally neutral story, and the other half of each group was exposed to a closely matched but more emotionally arousing story. The testing session consisted of a questionary containing 80 questions of multiple choices. The results were evaluated through percentage of correct answers. Results showed that correct answers were increased, in LTM measures, in the subjects that were given the emotional version of the test. In STM measures, no differences were found between the emotional and neutral version. However, the presentation of emotional story caused an emotional reaction in both groups. The lack of effect of emotional arousal in STM suggests that amygdala is not related to STM mechanisms. Further studies using different approaches are needed to elucidate if STM processes are influenced by emotional arousal.

Adolescent↗
PubMed2003

Epinephrine enhancement of human memory consolidation: interaction with arousal at encoding.

Abundant evidence indicates that endogenous stress hormones like epinephrine and cortisol modulate memory consolidation in animals. Despite this evidence, there has been no demonstration that endogenous stress hormones modulate memory consolidation in humans. In the present study, healthy subjects viewed a series of 21 slides, and immediately after received an intravenous infusion of either saline or epinephrine (40 or 80 ng/kg/min). Memory for the first three (primacy) and last three (recency) slides viewed was assessed with an incidental free recall test one week later. Epinephrine dose-dependently increased memory for the primacy slides, but did not affect memory of the recency slides. A subsequent experiment involving new subjects revealed significantly higher electrodermal responses to the primacy compared with recency slides. These findings support the view (Gold & McGaugh, 1975) that endogenous stress hormones modulate memory consolidation for experiences that induce their release. Additionally, they suggest that in humans these hormones may interact with the degree of arousal at initial encoding of information to modulate memory consolidation processes for that information.

Adult↗
PubMed2003

Modulation of memory consolidation for olfactory learning by reversible inactivation of the basolateral amygdala.

The role of the basolateral amygdala (BLA) in the consolidation of an association between an olfactory stimulus and footshock was investigated with a reversible lesion technique of post-training intra-BLA infusions of tetrodotoxin. Rats receiving tetrodotoxin infusions following paired odor-shock presentations spent more time near the odor, and reacted differently on contact with the odor when tested 24 hr after training, than did rats receiving paired presentations and saline infusions, but they did not differ from rats receiving unpaired presentations and saline infusions. The results indicate that the BLA plays a similar role in influencing consolidation of olfactory-based memory as it does for memory based on other modalities. Thus, these findings strengthen the view that the BLA plays a general role in modulation of memory storage for emotionally arousing events.

Amygdala↗
PubMed2003

Sex-related influences on the neurobiology of emotionally influenced memory.

In a recent report, the National Academy of Sciences concluded that "Sex matters. Sex, that is, being male or female, is an important basic human variable that should be considered when designing and analyzing studies in all areas and at all levels of biomedical and health-related research."(1) Recent findings from my laboratory concerning neural mechanisms of emotionally influenced memory further support this conclusion. This article first provides a brief, general overview of sex-related influences on brain and cognition. Upon this background, recent findings from my laboratory and others are described, demonstrating sex-related influences on neural mechanisms underlying emotionally influenced, explicit recall of emotionally arousing events. Both the hemispheric involvement of the human amygdala in memory for emotionally arousing events and the impairing effect of beta-adrenergic blockade on memory for emotional events exhibit pronounced sex-related differences. We interpret both of these effects in the context of evidence indicating hemispheric specialization in the processing of global/wholistic versus local/fine detail aspects of a situation. The more general conclusion that we draw from these investigations is that theories of the neurobiology of emotion and memory must begin to account for the seemingly substantial influences of sex.

Amygdala↗
PubMed2002

Pilot study of secondary prevention of posttraumatic stress disorder with propranolol.

BACKGROUND: Preclinical considerations suggest that treatment with a beta-adrenergic blocker following an acute psychologically traumatic event may reduce subsequent posttraumatic stress disorder (PTSD) symptoms. This pilot study addressed this hypothesis. METHODS: Patients were randomized to begin, within 6 hours of the event, a 10-day course of double-blind propranolol (n = 18) versus placebo (n = 23) 40 mg four times daily. RESULTS: The mean (SD) 1-month Clinician-Administered PTSD Scale (CAPS) score of 11 propranolol completers was 27.6 (15.7), with one outlier 5.2 SDs above the others' mean, and of 20 placebo completers, 35.5 (21.5), t = 1.1, df = 29, p =.15. Two propranolol patients' scores fell above, and nine below, the placebo group's median, p =.03 (sign test). Zero of eight propranolol, but six of 14 placebo, patients were physiologic responders during script-driven imagery of the traumatic event when tested 3 months afterward, p =.04 (all p values one-tailed). CONCLUSIONS: These pilot results suggest that acute, posttrauma propranolol may have a preventive effect on subsequent PTSD.

Accidents, Traffic↗
PubMed2002

Propranolol for reemergent posttraumatic stress disorder following an event of retraumatization: a case study.

This case report concerns a 44-year-old woman who experienced 5 similar motor vehicle accidents, the last 3 causing severe PTSD episodes of over 6 months each, despite multiple pharmacotherapies. Following a 6th accident, severe PTSD symptoms reemerged. Forty-eight hours after this trauma, propranolol (60 mg) orally, twice a day (1.75 mg/kg/day) was begun, and the PTSD symptoms were rapidly and markedly reduced. The Clinician-Administered PTSD Rating Scale score was reduced from an initial 86 to 56 by 11 days posttrauma. To our knowledge, this is the first report of the effects of propranolol treatment on reemergent PTSD symptoms. Propranolol may be particularly efficacious in the prevention of initial or reemergent PTSD symptoms.

Accidents, Traffic↗
PubMed2002

Relationship of enhanced norepinephrine activity during memory consolidation to enhanced long-term memory in humans.

OBJECTIVE: The purpose of this study was to investigate the effect of enhanced noradrenergic activity on memory consolidation in humans. METHOD: Thirty healthy subjects (21 men and nine women) viewed a series of 12 slides that depicted an emotionally arousing story. Five minutes after viewing the slides, subjects received either intravenous yohimbine or intravenous placebo in a double-blind randomized fashion. Multiple blood samples were drawn for determining plasma free 3-methoxy-4-hydroxyphenylglycol (MHPG). One week later subjects took a surprise memory test for the slides. RESULTS: There was no significant difference in memory score between yohimbine and placebo groups. Linear regression revealed a significant effect of MHPG on memory score for the group as a whole (subjects who had received yohimbine and those who had received placebo) and for the placebo group alone. CONCLUSIONS: These findings strengthen support for the hypothesis that enhanced memory for emotionally arousing events in humans depends critically on postlearning adrenergic modulation.

Adult↗
PubMedDate not supplied

Enhanced human memory consolidation with post-learning stress: interaction with the degree of arousal at encoding.

Abundant evidence indicates that endogenous stress hormones such as epinephrine and corticosterone modulate memory consolidation in animals. We recently provided the first demonstration that an endogenous stress hormone (epinephrine) can enhance human memory consolidation. However, these findings also suggested that post-learning stress hormone activation does not uniformly enhance memory for all recently acquired information; rather, that it interacts with the degree of arousal at initial encoding of material in modulating memory for the material. Here we tested this hypothesis by administering cold pressor stress (CPS) or a control procedure to subjects after they viewed slides of varying emotional content, and assessing memory for the slides 1 wk later. CPS, which significantly elevated salivary cortisol levels, enhanced memory for emotionally arousing slides compared with the controls, but did not affect memory for relatively neutral slides. These findings further support the view that post-learning stress hormone-related activity interacts with arousal at initial encoding to modulate memory consolidation.

Adult↗