Detection of Brain Activation in Unresponsive Patients with Acute Brain Injury.

BACKGROUND: Brain activation in response to spoken motor commands can be detected by electroencephalography (EEG) in clinically unresponsive patients. The prevalence and prognostic importance of a dissociation between commanded motor behavior and brain activation in the first few days after brain injury are not well understood. METHODS: We studied a prospective, consecutive series of patients in a single intensive care unit who had acute brain injury from a variety of causes and who were unresponsive to spoken commands, including some patients with the ability to localize painful stimuli or to fixate on or track visual stimuli. Machine learning was applied to EEG recordings to detect brain activation in response to commands that patients move their hands. The functional outcome at 12 months was determined with the Glasgow Outcome Scale-Extended (GOS-E; levels range from 1 to 8, with higher levels indicating better outcomes). RESULTS: A total of 16 of 104 unresponsive patients (15%) had brain activation detected by EEG at a median of 4 days after injury. The condition in 8 of these 16 patients (50%) and in 23 of 88 patients (26%) without brain activation improved such that they were able to follow commands before discharge. At 12 months, 7 of 16 patients (44%) with brain activation and 12 of 84 patients (14%) without brain activation had a GOS-E level of 4 or higher, denoting the ability to function independently for 8 hours (odds ratio, 4.6; 95% confidence interval, 1.2 to 17.1). CONCLUSIONS: A dissociation between the absence of behavioral responses to motor commands and the evidence of brain activation in response to these commands in EEG recordings was found in 15% of patients in a consecutive series of patients with acute brain injury. (Supported by the Dana Foundation and the James S. McDonnell Foundation.).

Flavor-intensity perception: effects of stimulus context.

Stimulus context affects judgments of intensity of both gustatory and olfactory flavors, and the contextual effects are modality-specific. Does context also exert separate effects on the gustatory and olfactory components of flavor mixtures? To answer this question, in each of 4 experiments, subjects rated the perceived intensity of 16 mixtures constructed by combining 4 concentrations of the gustatory flavorant sucrose with 4 concentrations of the retronasal olfactory flavorant citral. In 1 contextual condition of each experiment, concentrations of sucrose were relatively high and those of citral low; in the other condition, the relative concentrations of sucrose and citral reversed. There were 2 main results: First, consistent with earlier findings, in 5 of the 8 conditions, the ratings were consistent with linear addition of perceived sucrose and citral; departures from additivity appeared, however, in 3 conditions where the relative concentrations of citral were high. Second, changes in context produced contrast (adaptation-like changes) in perceived intensity: The contribution to perceived intensity of a given concentration of a flavorant was smaller when the contextual concentrations of that flavorant were high rather than low. A notable exception was the absence of contextual effects on the perceived intensity of near-threshold citral. These findings suggest that the contextual effects may arise separately in the gustatory and olfactory channels, prior to the integration of perceived flavor intensity.

Human flavor perception: Application of information integration theory.

The perception of flavor arises from the combination of inputs from several sensory modalities, especially gustation (taste proper) and olfaction (the primary source of flavor qualities). Both the perception of intensity of suprathreshold flavorants and, notably, the detection of weak flavorants are consistent with a rule of additivity. Thus, the detectability, d', of mixtures of the gustatory flavorant sucrose and the olfactory flavorant vanillin approximates the additive sum of detectabilities of the two components, within a model that assumes pooled noise in the flavor system that derives from both modalities. When gustatory and olfactory flavorants are presented in isolation, however, under conditions that encourage or permit selective attention to one modality or the other, it may be possible to filter out the noise associated with the unattended modality, and leading thereby to a rule of vector summation.

Social opportunity and ethanol drinking in rats.

Two experiments were designed to evaluate the effects of pairings of ethanol sipper conditioned stimulus (CS) with social opportunity unconditioned stimulus (US) on ethanol sipper CS-directed drinking in rats. In both experiments, rats were deprived of neither food nor water, and initiation of drinking of unsweetened 3% ethanol was evaluated, as were the effects of increasing the concentration of unsweetened ethanol (3-10%) across sessions. In Experiment 1, Group Paired (n=8) received 35 trials per session wherein the ethanol sipper CS was presented for 10 s immediately prior to 15 s of social opportunity US. All rats initiated sipper CS-directed drinking of 3% ethanol. Increasing the concentration of ethanol in the sipper CS [(3%, 4%, 6%, 8%, 10% (vol./vol.)] across sessions induced escalation of daily g/kg ethanol intake. To evaluate the hypothesis that the drinking in Group Paired was due to autoshaping, Experiment 2 included a pseudoconditioning control that received sipper CS and social opportunity US randomly with respect to one another. All rats in Group Paired (n=6) and in Group Random (n=6) initiated sipper CS-directed drinking of 3% ethanol and daily mean g/kg ethanol intake in the two groups was comparable. Also comparable was daily g/kg ethanol intake, which increased for both groups with the availability of higher concentrations of ethanol in the sipper CS, up to a maximum of approximately 0.8 g/kg ethanol intake of 10% ethanol. Results indicate that random presentations of ethanol sipper CS and social opportunity US induced reliable initiation and escalation of ethanol intake, and close temporally contiguous presentations of CS and US did not induce still additional ethanol intake. This may indicate that autoshaping CR performance is not induced by these procedures, or that high levels of ethanol intake induced by factors related to pseudoconditioning produces a ceiling effect. Implications for ethanol drinking in humans are discussed.

Effects of ethanol sipper and social opportunity on ethanol drinking in rats.

AIMS: The present study evaluates the effects of pairing ethanol sipper conditioned stimulus (CS) with social opportunity unconditioned stimulus (US) on CS-directed ethanol drinking in rats. Subjects were Long-Evans male rats (n = 32) deprived of neither food nor water, and the concentration of unsweetened ethanol (3 to 16%) in the sipper CS was increased across sessions. METHODS: Group Paired/Ethanol (n = 12) received the ethanol sipper CS for 10 s immediately prior to 15 s of social opportunity US. Control groups received water rather than ethanol in the sipper CS (Paired/Water), or ethanol sipper CS and US presentations randomly (Random/Ethanol), or ethanol sipper CS but no social opportunity US (Sipper Only). RESULTS: Mean ethanol intake in the Paired/Ethanol and Random/Ethanol groups exceeded 1.0 g/kg when the sipper CS contained 12%, 14% and 16% ethanol, and higher fluid intakes were observed in the Paired/Ethanol and Random/Ethanol groups than in the Paired/Water and Sipper Only groups. CONCLUSIONS: Social opportunity increased ethanol drinking, and more so than water drinking; however, autoshaping did not induce additional ethanol drinking beyond that observed in random controls.