Case report: neurochemical, physiological, and behavioral effects of bright light therapy on a cortically blind patient.

The present study evaluated the effects of bright light therapy on a patient with cortical blindness. Behavioral indices of functioning included the appraisal of mood, fatigue, appetite and orientation. Physiological measures assessed were blood pressure and temperature. Blood serum samples were analyzed for 5-HIAA and norepinephrine (NE). For the control and follow-up, the patient was exposed to 30 minutes of red light (300-lux), and thirty minutes of white light (10,000-lux) was used for treatment. High-pressure liquid chromatography analyses of blood serum samples revealed no change in serotonin (5-HT). However, an increase in blood NE was indicated following light treatment (red light: 12.7 ng/ml, white light: 43.5 ng/ml and, red light: 27.5 ng/ml). Analysis of data revealed significant differences in baseline and treatment scores for 4 of the outcome measures.

The effects on schedule-induced attack of covarying meal size and spacing.

Pigeons were exposed to fixed-time food schedules of 30, 120, and 480 sec with two reinforcer magnitudes at each. Attack behavior against a rear-projected conspecific image was assessed at each interfood/reinforcer magnitude combination. For seven of eight subjects, attack rate was related to interfood interval by an inverted-U or bitonic function. The larger reinforcer magnitude typically induced more attack than the smaller.

Injected testosterone fails to influence schedule-induced attack.

Three pigeons attacked a rear-projected conspecific target during exposure to a response-independent Fixed-Time 120 sec (FT 120 sec) and food delivery schedule. After baseline attack rates were established, subjects experienced two conditions in which they received injections (IM) of testosterone (10 mg and 20 mg; 100 mg/ml, in suspension) twenty minutes before session start. No concomitant change in attack rate or temporal location of attack was observed. Findings support observations suggesting that social context is an important determiner of the effects of testosterone on aggressive behavior.

Control of the temporal location of schedule-induced attack in pigeons.

Pigeons were exposed to complex fixed-ratio schedules to assess whether the temporal location of schedule-induced attack was controlled by the discriminative properties of food or by the aversive aftereffects of food withdrawal. When exposed to a multiple fixed-ratio 25 fixed-ratio N schedule in which either fixed-ratio component occurred with equal probability according to a quasi-random sequence and in which the value of N ranged from 115 to 150 across subjects, all pigeons exhibited post-food attack against a rear-projected conspecific target predominantly at the signalled onset of the higher-valued ratio component. Exposure of subjects to a mixed fixed-ratio 25 chained fixed-ratio 25 fixed-ratio N-25 schedule, however, resulted in a shift of attack to the signalled onset of the fixed-ratio N-25 component rather than following food. A chained fixed-ratio 25 fixed-ratio N-25 schedule induced attack predominantly after food delivery rather than at the onset of the fixed-ratio N-25 component. These findings show that the temporal locus of schedule-induced attack is primarily controlled by a stimulus, whether food delivery or key color change, that reliably precedes a relatively long period of reinforcer unavailability.

Effects of limited-target availability on schedule-induced attack.

Pigeons exposed to a 180-sec fixed-time food schedule could attack a rear-projected conspecific target that was available either (a) continuously throughout the interfood interval, (b) randomly during one 30-sec portion of each interfood interval, or (c) during the final 90 sec of each interval. During continuous-target availability, attack was maximal shortly after food ingestion and progressively decreased thereafter. During random-target availability, five of seven pigeons attacked less per target-access period the later that period occurred within the interfood interval, whereas two subjects exhibited relatively high local attack rates even when access periods occurred within the final third of the interval. When the target was available only during the second half of the interfood interval, attack occurred as soon as the target was presented and progressively decreased throughout the remainder of the target-access period. In general, these results show that schedule-induced attack can be increased by limiting the availability of that target and also indicate that such attack can reliably occur at times other than shortly after food delivery.

The effects of two response-elimination procedures on reinforced and induced aggression.

Pecks against a stuffed pigeon were reinforced according to a fixed-interval schedule for one group of pigeons and a variable-interval schedule for a second group. Red and green stimulus lights were alternately illuminated. Subsequently, food deliveries no longer occurred during one color (extinction). In the presence of the other color, food was presented only when no attack occurred for 30 sec. When attack produced food, all pigeons generally exhibited characteristic fixed-interval or variable-interval response patterns. Two birds in each group frequently exhibited postreinforcement schedule-induced aggression. Attack was reduced to low levels at approximately the same rate by extinction and differential reinforcement of other behavior. For birds that had previously exhibited schedule-induced aggression the initial reduction of attack during the second experimental phase was followed by induced attack immediately after food delivery in the differential-reinforcement-of-other-behavior component and upon onset of the extinction component, Either extinction or differential reinforcement of other behavior may eliminate reinforced aggression but may be relatively ineffective for reducing induced attack.

Effects of lick-contingent timeout on schedule-induced polydipsia.

Rats bar pressing on a 1-min fixed-interval schedule for 45-mg food pellets became polydipsic when water was concurrently available. They were then exposed to conditions in which each lick on the drinking tube produced a timeout period during which the food-schedule lever was retracted and the fixed-interval timer either did or did not continue to operate. Licks occurring within a timeout period extended its duration. As the duration of the lick-initiated timeout period was increased logarithmically through four values from 10 sec to 80 sec, lick rates as well as water intake rates generally decreased for all three subjects. As timeout duration was progressively increased, the rate of licks occurring in the absense of, but producing, timeouts decreased for all three rats, whereas the rate of licks occurring in the presence of timeout periods remained essentially constant. Water-intake rates and, with one exception, lick rates were suppressed more by timeout periods during which the fixed-interval timer did not continue to operate. These results indicate that lick-contingent timeout from positive reinforcement reduces schedule-induced drinking, and this suppressive effect is greater when the timeout period necessarily increases the interreinforcement interval beyond its minimum duration than when it does not.

Schedule-induced escape from fixed-interval reinforcement.

Pigeons trained to peck one of two keys for food were exposed to an ascending and descending series of fixed-interval values. A response on the second key produced an escape period consisting of a visual stimulus change. During escape periods, the fixed-interval timer continued to operate and even if it timed out, a response on the food key would not operate the feeder unless preceded by an escape-key response that terminated the escape condition. As the fixed-interval schedule was increased logarithmically through six values from 30 to 960 sec, the percentage of session time spent in escape as well as the frequency, duration, and rate of escape increased to a maximum and then decreased. One subject did not develop escape behavior to any significant degree. For all pigeons, escapes usually occurred after, rather than before, reinforcement.