Blocks Of Sessions Research Articles

Progress toward motor recovery with active neuromuscular stimulation: muscle activation pattern evidence after a stroke

Chronic cerebrovascular accident individuals with partial paralysis in an upper extremity typically demonstrate difficulty in voluntarily controlling movement initiation. This study investigated patterns of electromyogram (EMG) activation levels while stroke subjects voluntarily initiated their impaired wrist and finger extensor muscles. Twenty subjects were randomly assigned to either a unilateral movement/stimulation group or a bilateral movement/stimulation group. Participants completed 4 days (6 h over 2 weeks) of active neuromuscular stimulation (i.e., 5 s/trial, 90 trials/day, biphasic waveform) on the wrist and finger extensors according to group assignments. The EMG activation levels were analyzed with a three-factor mixed design Motor recovery protocol×Session block×Trial block (2×2×3) ANOVA with repeated measures on the second and third factors. This robust analysis revealed higher EMG activation levels for the coupled bilateral movement/stimulation group than the unilateral movement/stimulation group. In addition, higher muscle activation levels were found for the second session block as well as trial blocks 2 and 3. Overall, these findings indicated improved motor capabilities of the impaired muscles as evidenced by the higher voluntary EMG activation levels.

Reliability estimates for the immediate and delayed memory tasks.

The Immediate and Delayed Memory Tasks are variations of the Continuous Performance Test. While previous research with the tasks has focused on group performance across multiple blocks and sessions, reliability estimates have not been established. We estimated reliability (1) between blocks of a single testing session (N=106), (2) across four sessions within a single testing day (N=20), and (3) across sessions on four consecutive testing days (N=20). Analyses indicated that the primary variable of interest, i.e., commission of errors, showed acceptable reliability within and across testing periods.

Effects of reinforcement magnitude and ratio values on behaviour maintained by a cyclic ratio schedule of reinforcement.

In Experiments 1 and 2, lever pressing by rats was reinforced on a cyclic ratio schedule of food reinforcement, comprising a repeated sequence of fixed-ratio component schedules. Reinforcement magnitude was varied, on occasional sessions in Experiment 1 and across blocks of sessions in Experiment 2, from one to two or three 45-mg food pellets. In the one-pellet condition, post-reinforcement pauses increased with component schedule value. At higher magnitudes, post-reinforcement pauses increased, and overall response rates declined. Response rate on component schedules was a decreasing linear function of the obtained rate of reinforcement in all conditions. Plotted against component schedule value, response rate increased exponentially to an asymptote that decreased when reinforcement magnitude increased. These findings are consistent with regulatory accounts of food-reinforced behaviour. In Experiment 3, rats were trained under a cyclic ratio schedule comprising fixed-ratio components including higher values, and some inverted U-shaped response functions were obtained. Those rats that did not show this relationship were trained on cyclic ratios with even higher values, and all showed inverted U-shaped response functions. This suggests that behaviour on cyclic ratio schedules can reflect activating of reinforcement as well as the satiating effects seen in Experiments 1 and 2.

Effects of reinforcement magnitude and ratio values on behaviour maintained by a cyclic ratio schedule of reinforcement

In Experiments 1 and 2, lever pressing by rats was reinforced on a cyclic ratio schedule of food reinforcement, comprising a repeated sequence of fixed-ratio component schedules. Reinforcement magnitude was varied, on occasional sessions in Experiment 1 and across blocks of sessions in Experiment 2, from one to two or three 45-mg food pellets. In the one-pellet condition, post-reinforcement pauses increased with component schedule value. At higher magnitudes, post-reinforcement pauses increased, and overall response rates declined. Response rate on component schedules was a decreasing linear function of the obtained rate of reinforcement in all conditions. Plotted against component schedule value, response rate increased exponentially to an asymptote that decreased when reinforcement magnitude increased. These findings are consistent with regulatory accounts of food reinforced behaviour. In Experiment 3, rats were trained under a cyclic ratio schedule comprising fixed-ratio components including higher values, and some inverted U-shaped response functions were obtained. Those rats that did not showthis relationship were trained on cyclic ratios with even higher values, and all showed inverted U-shaped response functions. This suggests that behaviour on cyclic ratio schedules can reflect activating of reinforcement as well as the satiating effects seen in Experiments 1 and 2.

Lever-press responding maintained by contingent intraperitoneal administration of etonitazene in Long Evans hooded rats

Lever pressing maintained by intraperitoneal (IP) injections of etonitazene was established in five Long Evans hooded rats. Each training session consisted of an 8-min fixed interval (FI) during which lever pressing was maintained by food pellets delivered at the end of the interval. Food delivery was accompanied by illumination of stimulus lights in the chamber. Every 20th response during the 8 min interval also produced a brief illumination of the stimulus lights (FI 8 min (FR 20:S)). Administration of etonitazene was then introduced. Immediately following food delivery, the rat received an IP drug injection and was returned to the operant chamber for 30 min. During this confinement, the stimulus lights remained illuminated. This procedure resembles conditioned place preference in that an environment is paired with the effects of an investigator-delivered drug. When food pellet delivery subsequently was discontinued, responding persisted when followed by drug, but not saline, administration. Alternating blocks of sessions with administration of etonitazene (6.0–9.0 μg/kg) or saline produced corresponding increases or decreases in responding. These results indicate that etonitazene can function as a reinforcer when administered to rats by the IP route, and thus extend the range of conditions under which drug reinforcement can be investigated.

BEHAVIORAL MOMENTUM: THE EFFECTS OF THE TEMPORAL SEPARATION OF RATES OF REINFORCEMENT

In Part 1 of the experiment, rats responded under a variable-interval (VI) 30-s schedule and a VI 120-s schedule, with each in effect for a block of consecutive sessions. That is, the two VI schedules were presented in successive conditions. In Part 2 the VI schedules alternated each day, and in Part 3 the schedules alternated within the session as a multiple schedule. For half of the rats in Parts 1 and 2, the VI schedule alternated every few minutes within the session with a stimulus that signaled extinction. For each part, once response rates had stabilized, resistance to change was measured by prefeeding and extinction. When the schedules were examined in successive conditions (Part 1), resistance to extinction was greater under the VI 120-s schedule of reinforcement than under the VI 30-s schedule, but no consistent differences in resistance to prefeeding were observed between the two VI schedules. When the VI schedules alternated each day (Part 2), resistance to extinction was greater under the VI 120-s schedule. However, no consistent differences in resistance to prefeeding were observed between the VI schedules without extinction in Group A, but resistance to prefeeding was greater under the VI 30-s schedule for rats with the added extinction component in Group B. When the VI schedules alternated within the session as a multiple schedule (Part 3), resistance to extinction and resistance to prefeeding were greater under the VI 30-s schedule. The data suggest that different rates of reinforcement, and their accompanying discriminative stimuli, must be compared within the same session (or at least on alternate days) to produce data consistent with the behavioral momentum model.

Presession noise increases sensitivity to chlordiazepoxide's discriminative stimulus in pigeons

1. 1. Pigeons were trained to discriminate chlordiazepoxide (CDP) from saline using two-key food reinforced drug discrimination procedures. Discriminative control by CDP was maintained despite extended training with vehicle-like doses of CDP, by using a modified “fading” procedure that provided for a mixture of drug discrimination training sessions preceded by an i.m. injection of either 8.0 mg/kg CDP, or a lower training dose of CDP (4.0, 2.8, 2. 0, 1.4, 1.0, 0.7, or 0.5 mg/kg CDP), or saline. The lower training dose was decreased across blocks of sessions. 2. 2. Four lower training doses (1.4, 1.0, 0.7, and 0.5 mg/kg CDP) were retrained, with 10 min of 98 dB of noise administered 75 min prior to each drug discrimination training session. Presession exposure to noise increased percent CDP-appropriate choices for each of the four lower training doses by 15–20% over those obtained previously. 3. 3. It is concluded that brief presession exposure to loud noise increases sensitivity to the discriminative stimulus effects of low training doses of CDP.

Intensification of punishment effects through exposure to prolonged, fixed-duration shocks: The role of shock cues as a stimulus for fear

Three experiments tested the hypotheses that (1) the onsets of prolonged, fixed-duration treatment shocks (shock treatment, or ST) serve as cues for fear conditioning to the ongoing painful effects of these stimuli, and (2) this acquired fear transfers to and influences shock-motivated test performances in predictable ways. Experiments 1 and 2 involved spaced post-ST presentations of very brief shocks (a presumed analogue of the onsets of treatment shocks) as a means of extinguishing the fear putatively associated with shock cues. This procedure reduced defecation by ST subjects over blocks of extinction sessions and nullified the punishment intensification effect that was otherwise shown to be a consequence of ST. As a further test of the shock-cue hypothesis, Experiment 3 involved relatively massed presentations of these brief shocks prior to ST in a latent-inhibition procedure (Lubow, 1973). This briefshock regimen also nullified the ST punishment intensification effect but did not impair the transituational transfer of contextual fear. In contrast, the group that was given the same brief shock regimen following ST showed enhancement of the punishment effect. With respect to current theoretical accounts of ST effects, these data were most consistent with notions that rely on an acquired-fear construct.

Sources of Intertrial Proactive Interference in Rats’ Short-Term Memory in a Delayed Successive Matching-to-Sample Modality Discrimination

Rats were trained on a delayed successive matching-to-stimulus modality task consisting of onset of chamber lights or a tone for the sample stimulus, S1, and a comparison stimulus, S2. Lever pressing to S1 was reinforced as was lever pressing to its matching S2 (light–light or tone–tone pairs) but not to its mismatching S2 (light–tone, tone–light pairs). The interval between S1 and S2 within a trial, the retention interval (RI), was varied between 1 and 6 s within sessions while the interval between S2 and the next S1, the intertrial interval (ITI), was reduced from 24 to 12 s and finally to 6 s over blocks of sessions. In Experiment 1, where S1 was kept at 2 s and S2 at 10 s, rats’ matching accuracy declined over the longer RI, was slightly disrupted as ITIs were reduced to 6 s only over 1-s RIs, and was generally poorer to the tone than light S1. In Experiment 2, where both stimuli were 10 s increasing RIs caused steeper declines in matching accuracy to the tone S1 than light S1 and decreasing ITIs to 6 s disrupted rats performance over both RIs. Matching accuracy to the tone but not to the light S1 was also poorer when a preceding trial's S2 was a light S2 than when it was a tone S2 only during Experiment 2. Thisintertrial stimulus disagreementeffect was not influenced by ITI duration. These results suggest that intertrial proactive interference in delayed matching tasks consists of two separate and independent processes in rats similar to those found in pigeons (Edhouse & White, 1988).

Impact of tuning delay on the performance of bandwidth-limited optical broadcast networks with uniform traffic

This paper studies the effects of tuning delay of transmitters in packet-based optical broadcast networks. We consider scheduling of random traffic with tunable transmitters and fixed-tuned receivers and obtain the degradation imposed by tuning delay using several performance criteria, such as schedule completion time, average packet delay, and session blocking rates. We show that for off-line scheduling the effects of tuning delay are small even if the tuning time is as large as the packet duration. We provide a lower bound to the expected completion time of any off-line schedule with an arbitrary number of wavelengths. We then describe a near-optimal schedule which is based on the principle of having idle transmitters tune to wavelengths just-in-time to start their transmissions. Stability and capacity issues in the transmission of real-time traffic are considered and a queueing-theoretic analysis of average packet delay is given. The packet delay is found to be insensitive to tuning delay under near-optimal transmission scheduling. Finally we extend the model to connection-oriented networks and evaluate the session blocking performance for scheduled circuit connections.

The Relation between Variable-Interval Schedule Value and Subsequent Progressive-Ratio Persistence

The effect of variable-interval reinforcement rate on subsequent progressive-ratio responding was investigated by exposing five groups of rats to 15-session blocks of variable-interval training followed by a single progressive-ratio "test" session. Progressive-ratio test sessions began with a response requirement of 25 and incremented by 25 following each reinforcer. Sessions terminated when no responding occurred for 15 min. The reinforcement rate arranged by the variable-interval schedule was changed following exposure to each block of training and test sessions according to a Latin square design. Each subject received two blocks of training with variable-interval schedules arranging reinforcement rates of .25, .5, 1.0, 2.0, and 4.0 reinforcers per min. Response rates during the final five sessions of each variable-interval exposure was an increasing function of variable-interval reinforcement rate. Similarly, total responses emitted and response rate during progressive-ratio test sessions increased as a function of variable-interval reinforcement rate. In contrast, the amount of time required to satisfy the 15-min extinction criterion used to terminate test sessions decreased as variable-interval reinforcement rate increased. Similarly, the ratio of response rate during test sessions to the response rate during the five variable-interval sessions preceding the test was inversely related to the reinforcement rate arranged during the variable-interval sessions. Responding during test sessions persisted longer and response rate declined less following exposure to the lowest reinforcement rate variable-interval schedules than following the richer parameters. The use of occasional test sessions interpolated between blocks of training sessions is a promising method for assessing the relation among schedule parameters and performance under subsequent conditions.

Water deprivation-induced oral self-administration of cocaine in the Lewis rat: Evidence for locomotor effects but not reinforcement

Oral cocaine self-administration was studied in water-deprived Lewis rats. Liquid was available to rats only during daily 90-min sessions, in chambers equipped with spouts that delivered precise volumes of liquid following completion of lever-press responses. Blocks of training and testing sessions were alternately carried out during which increasing cocaine concentrations were presented: 0.0, 0.0125, 0.025, 0.05, 0.1, 0.2, 0.282, and 0.4 mg/ml. Although high cocaine intakes (23.3–33.0 mg/kg) were obtained, neither avoidance nor preference for cocaine developed. Subsequently, fixed-ratio size was increased, and then distinctive stimulus lights were correlated with each liquid. One rat showed a preference for water following these changes, but two rats continued to show no preference. To determine if the amounts of cocaine self-administered had behavioral effects, locomotor activity tests were run immediately following self-administration sessions. Locomotor activity was substantially higher following cocaine self-administration than following water self-administration. These results demonstrate that the cocaine intakes reached under the present conditions did produce locomotor, but not reinforcing, effects.

Analytic Group Therapy in Block Sessions: An Experience in Milan

Recent issues of Group Analysis have discussed what is now known as `block format' in group analysis. According to this model, the ninety- minute once-or twice-weekly sessions are replaced by blocks of sessions (ninety minutes each or longer), usually four per day, for two to five consecutive days, repeated at intervals of three weeks to six months. The on-going debate concerns two interrelated issues: (a) the advantages and disadvantages of the block model in training, and (b) its clinical and therapeutic viability. Here I concentrate on the second issue, drawing in particular on my experience in Milan, Italy. I would like to demonstrate that this way of working with people in groups has therapeutic validity.

Orally self-administered cocaine in rhesus monkeys: transition from negative or neutral behavioral effects to positive reinforcing effects

The establishment of orally delivered cocaine as a reinforcer was examined with nine rhesus monkeys. A 2% ethanol solution served as a reinforcer for all nine monkeys, for it maintained substantially higher response rates than did the concurrently available water vehicle. A test was initially conducted to determine whether cocaine would function as a reinforcer when substituted for 2% ethanol. When an intermediate cocaine concentration (0.2 mg/ml) was substituted for the ethanol solution, the drug maintained behavior at rates less than (seven monkeys), equal to (one monkey), or greater than (one monkey) those maintained by water. Thus, for eight of nine monkeys simple substitution of cocaine for ethanol was not sufficient to establish orally delivered cocaine as a reinforcer. In the next phase a stimulus-fading procedure was used. Blocks of training and testing sessions alternated. Across blocks of training sessions, increasing amounts of cocaine (0.0125, 0.025, 0.05, 0.1 mg/ml) were added to the 2% ethanol solution and subsequently the ethanol concentration was gradually decreased until only the 0.1 mg/ml cocaine solution remained; water was always concurrently available. Between each block of training sessions, a block of test sessions was inserted. Test sessions compared relative rates of responding maintained by two concurrently available drug solutions: (1) a solution containing the combination of ethanol and cocaine used in the prior training block and (2) a solution containing the same concentration of ethanol but with no cocaine. Thus, differences in rates of behavior maintained by the two solutions could be attributed to the presence of cocaine and the existence and degree of any such differences could be monitored at each step in the acquisition procedure. The outcome of the training procedure was that cocaine came to function as a reinforcer for six of the eight monkeys tested (the ninth monkey was not put through the fading procedure, having shown higher cocaine than vehicle rates during the initial substitution procedure). During the phase when ethanol was faded from the drug solution, differences between the combination cocaine-ethanol solution and the ethanol-only solution emerged: for the six monkeys that developed cocaine reinforced behavior, the combination solution maintained higher rates of responding than the ethanol solution alone. The opposite results were obtained with the remaining two monkeys. That cocaine had been established as a reinforcer was confirmed by persistent and orderly responding when dose and fixed-ratio size were subsequently varied.

Rats remember not wisely but too well

Rats were trained in a three-alternative spatial delayed matching-to-sample task in a starburst maze. Samples consisted of rewarded forced choices of one arm, and retention was indicated by rats’ returning to that arm after a 90-sec delay. If a rat made an error on its first choice, it was returned to the start compartment and allowed a second choice. Unlike in previous experiments with this task, all three arms were available during the animals’ second choices. The rats tended to perseverate in their second choices by returning to the arm that they had erroneously visited on their first choice. In Experiment 1, the accuracy of second choices following first-choice errors was below chance during the first block of sessions, when a 90-sec delay intervened between the first choice and the second choice, and at chance during the second block of sessions, when a short (5–6 see) delay intervened between first and second choices. In Experiment 2, long-delay and short-delay sessions were randomly presented to naive subjects. Similar results were obtained. In both experiments, the tendency to repeat the erroneous first choice was greater when long delays separated the two choices than when short delays were used. The results suggest that rats make their first-choice errors because they erroneously encode or remember the location of the sample and that they base their second choices on the same erroneous-memory. The increase in perseveration at long delays implies some kind of rehearsal-like mechanism that slows forgetting of the memory controlling the first choice.

Oral self-administration of pentobarbital by rhesus monkeys: relative reinforcing effects under concurrent signalled differential-reinforcement-of-low-rates schedules

During daily 3-h sessions two separate pentobarbital solutions were concurrently available to rhesus monkeys under signalled differential-reinforcement-of-low-rates (signalled DRL) schedules of mouth contacts with spouts. The schedules were synchronized so that each time the 30-s DRL interval expired, lights above both spouts were illuminated and a liquid delivery could be obtained either from the left or right spout, but not both. First water and then each of four ‘comparison-concentration’ pentobarbital solutions (0.0625, 0.25, 1 and 4 mg/ml) were successively available under one schedule for a block of sessions. Concurrently, deliveries of a ‘standard concentration’ solution were available from the second spout under an identical DRL schedule; the concentration of this standard solution remained constant throughout the testing of the series of comparison solutions. Three pentobarbital concentrations (4, 1 and 0.25 mg/ml) in turn served as the standard concentration. Relative reinforcing effects were directly related to pentobarbital concentration: in general, within pairs of concurrently available pentobarbital solutions more behavior was maintained by the higher of the two drug concentrations. These findings are discussed in the context of previous studies using ratio and interval schedules which have found relative reinforcing effects to be directly related to reinforcer magnitude.

Choice in situations of time-based diminishing returns: immediate versus delayed consequences of action.

Pigeons chose between two schedules of food presentation, a fixed-interval schedule and a progressive-interval schedule that began at 0 s and increased by 20 s with each food delivery provided by that schedule. Choosing one schedule disabled the alternate schedule and stimuli until the requirements of the chosen schedule were satisfied, at which point both schedules were again made available. Fixed-interval duration remained constant within individual sessions but varied across conditions. Under reset conditions, completing the fixed-interval schedule not only produced food but also reset the progressive interval to its minimum. Blocks of sessions under the reset procedure were interspersed with sessions under a no-reset procedure, in which the progressive schedule value increased independent of fixed-interval choices. Median points of switching from the progressive to the fixed schedule varied systematically with fixed-interval value, and were consistently lower during reset than during no-reset conditions. Under the latter, each subject's choices of the progressive-interval schedule persisted beyond the point at which its requirements equaled those of the fixed-interval schedule at all but the highest fixed-interval value. Under the reset procedure, switching occurred at or prior to that equality point. These results qualitatively confirm molar analyses of schedule preference and some versions of optimality theory, but they are more adequately characterized by a model of schedule preference based on the cumulated values of multiple reinforcers, weighted in inverse proportion to the delay between the choice and each successive reinforcer.

Long-term Retention of Implicitly Acquired Learning in Patients with Alzheimer's Disease

This study examined retention of procedural learning, using the serial reaction time (SRT) task, over a 1- or 2-week delay in Alzheimer's disease (AD) patients and elderly control (EC) subjects. The SRT task is a four-choice reaction-time task consisting of blocks of 100 trials. A 10-item repeating sequence was embedded in the first four blocks of trials in session one and the first two blocks of session two. Sequence-specific learning was assessed in session one by comparing reaction time (RT) in the fourth block with a repeating sequence to a fifth block in session one in which the stimuli were randomly arranged. After excluding subjects with deficient session one learning, there were eight AD patients and 14 EC subjects who showed robust sequence-specific learning in session one. In these subjects, retention of sequence-specific learning over the 1- to 2-week delay was examined. The AD patients and EC subjects showed an equivalent change in RT across sessions, and all the AD patients lacked any declarative knowledge of the repeating sequence within the task. Individually, two of the eight AD patients appeared to deviate substantially from the others and from the EC subjects in their excess slowing of RT across sessions. Since six AD patients did show retention similar to the EC subjects, it is concluded that at least some AD patients show normal retention of implicitly acquired knowledge over a long delay. Preserved retention in some of the AD patients implies that it is mediated by brain structures that are not affected by the Alzheimer neuropathological process.

Using a clicker and a tone CS to suppress free-operant avoidance behavior

Rats were trained under a free-operant avoidance schedule with R-S intervals of 15, 20, or 30 sec. Following a repeated-measures design, the rats received a 60-sec clicking and discontinuous-tone stimulus as a preshock CS in separate training phases. Each block of CS-US sessions was preceded and followed by blocks of CS sessions without the US. The two preshock CSs produced comparable levels of suppressed avoidance behavior, as indexed by an increase in rates of unavoided shocks. The CS-US arrangements failed to produce significant differences between response-rate measures. Reliable differences in indexes of suppressed avoidance due to either the R-S interval or the kind of auditory CS were not found. However, enhancement in avoidance behavior occurred during the clicking CS in the pretest sessions.

Goal-directed speech in a spoken language system

The advent of reliable speaker-independent continuous speech recognition systems has made it possible to design systems that use speech as a replacement for keyboard input. To understand the nature of a system that accepts spontaneous goal-directed speech (as opposed to the current standard of read speech), a spoken-language spreadsheet was implemented and users performing a series of tasks using this system were studied. The system was instrumented to allow the collection of detailed timing information about the components of the interaction cycle. The (HMM-based) recognition system incorporates a lexicon of 273 words and a language of perplexity 51. Four users performed a series of 40 tasks (involving the entry of personal financial information) alternating voice and keyboard input. Users completed 30 tasks in one block of sessions, then returned a month later to complete the remainder. The utterances spoken into the system (over 7500) were stored for later analysis. The data collected provide a comprehensive picture of how users learn to use a spoken-language system and provide an understanding of the factors that govern performance in spoken-language systems.