PubMed Health⌕ Search

Biomedical subjects

A Bechara

Publications and source records attributed to A Bechara.

At least 19 recordsLinked to original sources
PubMed2006

Cognitive function and mood in MDMA/THC users, THC users and non-drug using controls.

Repeated ecstasy (MDMA) use is reported to impair cognition and cause increased feelings of depression and anxiety. Yet, many relevant studies have failed to control for use of drugs other than MDMA, especially marijuana (THC). To address these confounding effects we compared behavioural performance of 11 MDMA/THC users, 15 THC users and 15 non-drug users matched for age and intellect. We tested the hypothesis that reported feelings of depression and anxiety and cognitive impairment (memory, executive function and decision making) are more severe in MDMA/THC users than in THC users. MDMA/THC users reported more intense feelings of depression and anxiety than THC users and non-drug users. Memory function was impaired in both groups of drug users. MDMA/THC users showed slower psychomotor speed and less mental flexibility than non-drug users. THC users exhibited less mental flexibility and performed worse on the decision making task compared to non-drug users but these functions were similar to those in MDMA/THC users. It was concluded that MDMA use is associated with increased feelings of depression and anxiety compared to THC users and non-drug users. THC users were impaired in some cognitive abilities to the same degree as MDMA/THC users, suggesting that some cognitive impairment attributed to MDMA is more likely due to concurrent THC use.

Adult↗
PubMed2005

Impaired perception of self-motion (heading) in abstinent ecstasy and marijuana users.

RATIONALE: Illicit drug use can increase driver crash risk due to loss of control over vehicle trajectory. This study asks, does recreational use of +/-3,4-Methylenedioxymethamphetamine (MDMA; ecstasy) and tetrahydrocannabinol (THC; marijuana) impair cognitive processes that help direct our safe movement through the world? OBJECTIVE: This study assesses the residual effects of combined MDMA/THC use, and of THC use alone, upon perceived trajectory of travel. METHODS: Perception of self-motion, or heading, from optical flow patterns was assessed using stimuli comprising random dot ground planes presented at three different densities and eight heading angles (1, 2, 4 and 8 degrees to the left or right). On each trial, subjects reported if direction of travel was to the left or the right. RESULTS: Results showed impairments in both drug groups, with the MDMA/THC group performing the worst. CONCLUSIONS: The finding that these psychoactive agents adversely affect heading perception, even in recently abstinent users, raises potential concerns about MDMA use and driving ability.

Adult↗
PubMed2005

The ability to decide advantageously declines prematurely in some normal older persons.

The prefrontal region of the brain, including the ventromedial sector which supports reasoning and decision-making, may undergo disproportionate aging in some older persons, but the empirical evidence is decidedly mixed. To help resolve this, we tested 80 neurologically and psychiatrically healthy Younger (aged 26-55) and Older (aged 56-85) adults on a "Gambling Task", which provides a close analog to real-world decision-making by factoring in reward, punishment, and unpredictability, yielding a sensitive index of ventromedial prefrontal function. A subset of the Older group manifested a decision-making impairment on the Gambling Task, in spite of otherwise intact cognitive functioning. This finding raises the possibility of disproportionate aging of the ventromedial prefrontal cortex in these individuals. Our finding has important societal and public policy implications (e.g., choosing medical care, allocating personal wealth), and may also help explain why many older individuals are targeted by and susceptible to fraudulent advertising.

Adult↗
PubMed2005

The Iowa Gambling Task and the somatic marker hypothesis: some questions and answers.

A recent study by Maia and McClelland on participants' knowledge in the Iowa Gambling Task suggests a different interpretation for an experiment we reported in 1997. The authors use their results to question the evidence for the somatic marker hypothesis. Here we consider whether the authors' conclusions are justified.

Adaptation, Psychological↗
PubMed2003

Duplex Doppler ultrasound assessment of clitoral hemodynamics after topical administration of alprostadil in women with arousal and orgasmic disorders.

There are limited hemodynamic data in women with arousal or orgasmic disorders and even fewer normative control hemodynamic data in women without sexual dysfunction. In addition, there is limited experience with topical vasoactive agents (used to maximize genital smooth muscle relaxation) applied to the external genitalia during hemodynamic evaluations. The aim of this study was to report duplex Doppler ultrasound clitoral cavernosal arterial changes before and after topical PGE-1 (Alprostadil) administration in control women and in patients with arousal and orgasmic sexual disorders. We found that women with sexual arousal and orgasmic disorders had significantly (p < 0.05) diminished clitoral peak systolic and end diastolic velocity responses compared to controls. Further research is needed to establish the diagnostic role of topical vasoactive agents in the hemodynamic evaluation of women with sexual dysfunction.

Administration, Topical↗
PubMed2001

Decision-making deficits, linked to a dysfunctional ventromedial prefrontal cortex, revealed in alcohol and stimulant abusers.

A decision-making instrument known as the "gambling task" was used, which has been shown to be sensitive to the decision-making impairment of patients with bilateral lesions of the ventromedial prefrontal cortex (VM). Three groups of subjects were tested, substance dependent individuals (SD) (n=41), normal controls (n=40), and VM patients (n=5). All SD met the DSM-IV criteria for dependence, with either alcohol or stimulants (metamphetamine or cocaine) as the primary substance of choice. The results revealed a significant impairment in the performance of SD relative to normal controls. A significantly high proportion of SD (61 vs. only 32.5% of normal controls) performed within the range of the VM patients, while the rest performed within the range of normal controls. General demographic factors such as age, sex, and level of education could not explain these differences in performance. As well, differences in performance were not explained by intelligence (IQ), memory, or performance on standard executive function/frontal lobe tests. Performance on the gambling task was best predicted by a combination of factors, including duration of abstinence, years of abuse, relapses and times in treatment, and the ability to hold gainful employment. The results support the hypothesis that impairment in decision-making linked to a dysfunctional VM cortex is associated with at least a sub-group of SD.

Adult↗
PubMed2001

Neurobiology of decision-making: risk and reward.

Neurological patients with bilateral ventromedial (VM) lesions of the prefrontal cortex often deny, or they are not aware that they have a problem. Furthermore, they often pursue actions that bring some reward in the immediate run, despite severe long-term consequences such as the loss of job, home, and family. The somatic marker hypothesis, which provides an account of this defect in decision-making, posits that the impairment is the result of defective activation of somatic markers that normally function as covert or overt signposts for helping with the process of making choices that are advantageous to the organism. Failure to enact somatic states results from dysfunction in a neural system in which the VM cortex is one critical region. However, other neural regions, including the amygdala, and somatosensory cortices (SI, SII, and insula) are also hypothesized to be components of that same neural system. Recent evidence reveals that substance abusers suffer from decision-making deficit akin to that seen with patients with VM lesions. Thus, the strategies used to study decision-making in neurological patients have direct implications for understanding several neuropsychiatric disorders including addiction and pathological gambling.

Amygdala↗
PubMed2000

Subcortical and cortical brain activity during the feeling of self-generated emotions.

In a series of [15O]PET experiments aimed at investigating the neural basis of emotion and feeling, 41 normal subjects recalled and re-experienced personal life episodes marked by sadness, happiness, anger or fear. We tested the hypothesis that the process of feeling emotions requires the participation of brain regions, such as the somatosensory cortices and the upper brainstem nuclei, that are involved in the mapping and/or regulation of internal organism states. Such areas were indeed engaged, underscoring the close relationship between emotion and homeostasis. The findings also lend support to the idea that the subjective process of feeling emotions is partly grounded in dynamic neural maps, which represent several aspects of the organism's continuously changing internal state.

Action Potentials↗
PubMed2000

Characterization of the decision-making deficit of patients with ventromedial prefrontal cortex lesions.

On a gambling task that models real-life decisions, patients with bilateral lesions of the ventromedial prefrontal cortex (VM) opt for choices that yield high immediate gains in spite of higher future losses. In this study, we addressed three possibilities that may account for this behaviour: (i) hypersensitivity to reward; (ii) insensitivity to punishment; and (iii) insensitivity to future consequences, such that behaviour is always guided by immediate prospects. For this purpose, we designed a variant of the original gambling task in which the advantageous decks yielded high immediate punishment but even higher future reward. The disadvantageous decks yielded low immediate punishment but even lower future reward. We measured the skin conductance responses (SCRs) of subjects after they had received a reward or punishment. Patients with VM lesions opted for the disadvantageous decks in both the original and variant versions of the gambling task. The SCRs of VM lesion patients after they had received a reward or punishment were not significantly different from those of controls. In a second experiment, we investigated whether increasing the delayed punishment in the disadvantageous decks of the original task or decreasing the delayed reward in the disadvantageous decks of the variant task would shift the behaviour of VM lesion patients towards an advantageous strategy. Both manipulations failed to shift the behaviour of VM lesion patients away from the disadvantageous decks. These results suggest that patients with VM lesions are insensitive to future consequences, positive or negative, and are primarily guided by immediate prospects. This 'myopia for the future' in VM lesion patients persists in the face of severe adverse consequences, i.e. rising future punishment or declining future reward.

Adult↗
PubMed2000

Emotion, decision making and the orbitofrontal cortex.

The somatic marker hypothesis provides a systems-level neuroanatomical and cognitive framework for decision making and the influence on it by emotion. The key idea of this hypothesis is that decision making is a process that is influenced by marker signals that arise in bioregulatory processes, including those that express themselves in emotions and feelings. This influence can occur at multiple levels of operation, some of which occur consciously and some of which occur non-consciously. Here we review studies that confirm various predictions from the hypothesis. The orbitofrontal cortex represents one critical structure in a neural system subserving decision making. Decision making is not mediated by the orbitofrontal cortex alone, but arises from large-scale systems that include other cortical and subcortical components. Such structures include the amygdala, the somatosensory/insular cortices and the peripheral nervous system. Here we focus only on the role of the orbitofrontal cortex in decision making and emotional processing, and the relationship between emotion, decision making and other cognitive functions of the frontal lobe, namely working memory.

Animals↗
PubMed1999

Different contributions of the human amygdala and ventromedial prefrontal cortex to decision-making.

The somatic marker hypothesis proposes that decision-making is a process that depends on emotion. Studies have shown that damage of the ventromedial prefrontal (VMF) cortex precludes the ability to use somatic (emotional) signals that are necessary for guiding decisions in the advantageous direction. However, given the role of the amygdala in emotional processing, we asked whether amygdala damage also would interfere with decision-making. Furthermore, we asked whether there might be a difference between the roles that the amygdala and VMF cortex play in decision-making. To address these two questions, we studied a group of patients with bilateral amygdala, but not VMF, damage and a group of patients with bilateral VMF, but not amygdala, damage. We used the "gambling task" to measure decision-making performance and electrodermal activity (skin conductance responses, SCR) as an index of somatic state activation. All patients, those with amygdala damage as well as those with VMF damage, were (1) impaired on the gambling task and (2) unable to develop anticipatory SCRs while they pondered risky choices. However, VMF patients were able to generate SCRs when they received a reward or a punishment (play money), whereas amygdala patients failed to do so. In a Pavlovian conditioning experiment the VMF patients acquired a conditioned SCR to visual stimuli paired with an aversive loud sound, whereas amygdala patients failed to do so. The results suggest that amygdala damage is associated with impairment in decision-making and that the roles played by the amygdala and VMF in decision-making are different.

Acoustic Stimulation↗
PubMed1999

Impairment of social and moral behavior related to early damage in human prefrontal cortex.

The long-term consequences of early prefrontal cortex lesions occurring before 16 months were investigated in two adults. As is the case when such damage occurs in adulthood, the two early-onset patients had severely impaired social behavior despite normal basic cognitive abilities, and showed insensitivity to future consequences of decisions, defective autonomic responses to punishment contingencies and failure to respond to behavioral interventions. Unlike adult-onset patients, however, the two patients had defective social and moral reasoning, suggesting that the acquisition of complex social conventions and moral rules had been impaired. Thus early-onset prefrontal damage resulted in a syndrome resembling psychopathy.

Adult↗
PubMed1998

Dissociation Of working memory from decision making within the human prefrontal cortex.

We tested the hypothesis that cognitive functions related to working memory (assessed with delay tasks) are distinct from those related to decision making (assessed with a gambling task), and that working memory and decision making depend in part on separate anatomical substrates. Normal controls (n = 21), subjects with lesions in the ventromedial (VM) (n = 9) or dorsolateral/high mesial (DL/M) prefrontal cortices (n = 10), performed on (1) modified delay tasks that assess working memory and (2) a gambling task designed to measure decision making. VM subjects with more anterior lesions (n = 4) performed defectively on the gambling but not the delay task. VM subjects with more posterior lesions (n = 5) were impaired on both tasks. Right DL/M subjects were impaired on the delay task but not the gambling task. Left DL/M subjects were not impaired on either task. The findings reveal a cognitive and anatomic double dissociation between deficits in decision making (anterior VM) and working memory (right DL/M). This presents the first direct evidence of such effects in humans using the lesion method and underscores the special importance of the VM prefrontal region in decision making, independent of a direct role in working memory.

Adult↗
PubMed1998

A two-separate-motivational-systems hypothesis of opioid addiction.

There has been a long debate as to whether opioids are sought for withdrawal relief or for their ability to serve as incentives in their own right. We suggest that independent motivational systems mediate the rewarding effects of opioids in the nondependent state and in the physically dependent/withdrawal state. In the opioid-dependent state and the presence of opioid withdrawal, the rewarding effects of withdrawal relief inhibit or mask the acute rewarding effects initially exerted in the nondependent state, but the acute rewarding effects are unmasked after the alleviation of withdrawal.

Animals↗
PubMed1998

Drop-out reasons and complications in self-injection therapy with a triple vasoactive drug mixture in sexual erectile dysfunction.

The usefulness, complications and reasons for discontinuing the self-injection program with a combination of papaverine, phentolamine and prostaglandin E1 were evaluated in 189 patients (mean age 57.2 y), who were included from April 1993 to September 1995 (mean follow-up 10.25 months). Patients were split into two groups: Active, those who continued with the program (48%); and Inactive, those who discontinued treatment or failed to attend consultation after five months from the last visit (52%). Only 30% of the inactive group reported failure to achieve response with the self-injected doses. Fibrosis in 5.3% and prolonged erection in 3.7% were the most severe complications. Patients lacking organic pathology showed a clear tendency to reduce the drug dose during treatment, recover spontaneous erections and discontinue the program for reasons unrelated to drug efficacy. The triple drug mixture provides an effective alternative in the treatment of impotence, with a low rate of complications.

Adult↗
PubMed1998

Clinical and physiological effects of stereotaxic bilateral amygdalotomy for intractable aggression.

The amygdala is thought to be an important neural structure underlying the "fight-or-flight" response, but information on its role in humans is scarce. The clinical and psychophysiological effects of amygdalar destruction were studied in 2 patients who underwent bilateral amygdalotomy for intractable aggression. After surgery, both patients showed a reduction in autonomic arousal levels to stressful stimuli and in the number of aggressive outbursts, although both patients continued to have difficulty controlling aggression. The "taming effect" reported after bilateral amygdalar destruction may be due to the amygdala's inadequate processing of perceived threat stimuli that would normally produce a fight-or-flight response.

Adult↗