Karen Herzig

A low dose of subcutaneous nicotine improves information processing in non-smokers

Many studies have found that cigarette smoking or nicotine improves mental functioning in abstinent smokers. An unresolved issue is whether this improvement is due primarily to a direct facilitation of performance or to relief of the impairment caused by nicotine withdrawal. We evaluated the performance of 12 non-smokers before and twice (15 and 45 min) after a subcutaneous injection of 0.8 mg nicotine, 0.8 ml saline, and a control no treatment, on a choice reaction time (RT) task. Each treatment was given on a separate day; the control day was given on the first session. The order of nicotine and saline was balanced between subjects, and injections were given double-blind. The RT task manipulated stimulus and response processing. These manipulations consisted of two levels of stimulus complexity and two levels of response complexity, resulting in four task conditions. These manipulations along with latency measures of the event-related potential were used to identify the components of processing that mediated nicotines effects on performance. During each active drug session blood nicotine levels, cardiovascular, and subjective responses were measured before and after each of the three tests (pre-drug, 15 min and 45 min post-drug). For the information processing measures only the comparisons of the pre- and 15-min post-test showed significant drug effects. Nicotine compared to saline significantly increased the number of responses at the fast end of the RT distribution. However, there were no changes in accuracy. Nicotine also speeded mean RT compared with saline or the control day, but the effects were only significant for the control-nicotine comparison. There was an interaction between effects of nicotine and the task variables, such that nicotine speeded P3 latency in the hardest task condition, while slowing it in the other task conditions. Nicotine significantly increased heart rate, which lasted for the entire session. Blood nicotine levels were lower than expected from a preliminary study in smokers and may have been responsible for the smaller than expected mean RT effects. These findings suggest that even a low dose of nicotine directly affects attention or stimulus processing components of information processing. This study also illustrates the importance of assessing both multiple components of information processing and nicotine levels when examining the effects of nicotine on cognition.

Effects of cotinine on information processing in nonsmokers.

Abstract Cotinine, the major proximate metabolite of nicotine, is present in smokers in higher concentrations and for a longer time than nicotine, yet its effects on information processing have not previously been reported. We studied the cognitive effects of cotinine in non-smokers. Sixteen subjects were tested on three doses of cotinine (0.5, 1.0, and 1.5 mg cotinine base/kg), and placebo, on a choice reaction time (RT) task and on a verbal recall task with short and long lists. Cotinine significantly impaired recall on the long list and displayed non-significant but generally consistent dose-related slowing of RT and N100 latency. The acute effects of cotinine were small, and probably do not account for the cognitive deficits observed in tobacco withdrawal, although the cognitive effects of chronic cotinine administration need to be investigated.

Drugs and human information processing

Human performance on a choice–reaction time task (Eriksen task) has been simulated by a neural network. In simulations, the network captures many features of normal performance. In addition, changing gain in different layers produces changes that simulate different drug-induced changes. Data from a similar choice–reaction time task have been reanalyzed to test some of the predictions derived from changing gain in different layers. Clonidine antagonizes norepinephrine and acetylcholine activities and changes speed–accuracy tradeoff (i.e., increased frequency of errors at any specified reaction time). That is predicted when gain is reduced in lower layers (attention layer and input layer) of the network. By contrast, manipulating dopamine activity (with pimozide and amphetamine) changes reaction time without changing speed–accuracy tradeoff functions. That is predicted when gain is changed in the output layer of the network.

The mysteries and demands of HIV care: qualitative analyses of HIV specialists' views on their expertise.

To deepen our understanding of the mysteries and demands associated with HIV care and to inform the debate about HIV specialization, we conducted in-depth interviews with a purposive sample of 20 identified HIV specialists in the San Francisco Bay Area. Participants were from several medical specialties and reported a median of 50% of their time spent in HIV patient care. Through constant comparison, a template of open codes was constructed to identify themes that emerged from the data. Data were analyzed according to the conventions of qualitative research and revealed six interrelated themes: (1) coping with uncertainty and rapid change: being ‘comfortable with mystery’; (2) the powerful role of experience; (3) the dual faces of knowledge: ‘knowing the patient’ and ‘knowing the facts’; (4) the dual faces of passion: challenge and calling; (5) stress and burnout; and (6) the relationship between academia and ‘the trenches’. The themes underscore the dual dimensions of HIV care: providers must interweave the ‘half-baked’ science about drug therapies, side effects and drug interactions with the psychosocial and lifestyle factors of the patient. They also provide insight into quantitative findings linking greater HIV experience with better patient outcomes and suggest that providers need skills associated with generalist and specialist training, a phenomenon that argues for a ‘special’ specialty for HIV care.

The effects of the human immunodeficiency virus on visual information processing

Only one study that we are aware of has examined subjects infected with human immunodeficiency virus (HIV) in the context of information processing, and that study was limited in that processing stages could only be inferred from reaction time (Perdices and Cooper 1989). By employing a visual reaction-time task while also measuring brain event-related potentials (ERPs), we obtained additional information that could be interpreted within the framework of an information processing model (Callaway 1984; Nayior et al 1987), and compared to non-information processing visual ERP studies of HIV-positive subjects. The purpose of our study was to determine whether we could identify information processing changes associated with HIVpositive status before onset of late-stage disease symptoms, i.e., before an acquired immune deficiency syndrome (AIDS) or AIDS dementia complex diagnosis. The ability to detect such changes could have important implications in the assessment of new drug therapies and the management of HIV-related cognitive dysfunction if such information reliably marks disease progression and/or predicts AIDS dementia complex development. Our secondary goal was to determine whether any information processing changes could be related to the known cognitive effects of a drug or class of drugs. If so, we might shed more light on the neurotransmitter system(s) most affected by the disease and possibly suggest a therapeutic substitution for its neurotransmitter deficiencies (Carlsson 1987).