Septohippocampal system and the prelimbic sector of frontal cortex: a neuropsychological battery analysis in the rat.

Rats with lesions in the posterodorsal septal area (aimed at transecting the precommissural fornix) and rats with lesions in the prelimbic sector of the medial frontal cortex were tested postoperatively on a neuropsychological test battery comprised of the following tasks: time-spent-eating in two adaptation boxes, time-to-emerge and ambulation in an open field, general activity, contingently-reinforced (continuous) and schedule-specific (delayed non-matching-to-sample) T-maze alternation, visual and olfactory discrimination in a T-maze, temporal alternation (response patterning) and tactile Go/No-Go discrimination in a runway, approach-avoidance conflict in the runway, step-through inhibitory avoidance, one-way active avoidance, two-way active avoidance, and conditioned taste aversion. It was found that: (1) rats with septal (SEP) lesions spent more time eating than control (CON) rats and rats with lesions in prelimbic cortex (PRE). PRE rats did not differ from CON rats; (2) PRE rats emerged into an open field faster, and spent less time in home cage than CON and SEP rats. SEP rats stayed in home cage less than CON rats. PRE and SEP rats crossed more squares in the open field than CON rats; (3) SEP and PRE rats were more active than CON rats; (4) SEP rats performed the contigently-reinforced and schedule-specific T-maze alternation tasks worse than PRE rats, and PRE rats performed these tasks worse than CON rats. PRE, but not SEP, rats showed improvement with continued practice at brief intertrial and interrun intervals.(ABSTRACT TRUNCATED AT 400 WORDS)

Lateral preferences in Brazilian adults: an analysis with the Edinburgh Inventory.

The lateral preferences of 959 Brazilian adults (471 males and 488 females) were assessed with the abbreviated form of the Edinburgh Inventory using the interview method. The behavioral validity of the inventory was evaluated by asking 36 subjects to perform the activities included in the inventory five months after the interview. The results showed that lateral preferences in Brazilian adults are similar to those reported from other countries. Additionally, effects of sex and age on hand preference were observed. However, area of professional occupation was not related to hand preference. Factor analysis of the Edinburgh Inventory (including items related to foot, eye and ear preference) revealed two factors. Factor I ("Motor-Related Laterality") included all handedness items and the foot-preference item, and Factor II ("Sensory-Related Laterality") included the eye and ear preference items. The Edinburgh Inventory was found to be reliable and valid in this population.

Lesions in the septo-hippocampal system or prelimbic cortex of rats do not alter the performance of a T-maze visual discrimination task but disrupt the performance of a T-maze alternation task.

Rats with lesions in the posterodorsal septum (SEP), prelimbic cortex (PRE), and control operations (CON) were tested in a continuous alternation task (intertrial interval, ITI = 0 s) and a visual discrimination task (ITI ca 100 s) in a T-maze. CON rats performed the alternation task significantly better than rats with SEP or PRE lesions. PRE rats, but not SEP rats, were able to master the task with continued practice. The three groups did not differ in performance of the visual discrimination task. These data suggest that the septo-hippocampal system and, to a lesser extent, the prelimbic cortex are specifically involved in the memory processes necessary for the performance of an alternation but not a visual discrimination task in a T-maze.

Locomotor activity and one-way active avoidance after intrahippocampal injection of neurotransmitter antagonists.

Sixty-three rats with previous training in a T-maze, bilaterally implanted with cannulae directed toward the dorsal hippocampus, were used in this study. All rats received bilateral 1-microliter injections 20 min before testing for locomotor activity (day 1) and one-way active avoidance (day 3). The following drugs were injected into groups of 4 to 8 animals: scopolamine (9 or 18 micrograms/microliters), propranolol (5 or 10 micrograms/microliters), cimetidine (0.75 or 1.5 micrograms/microliters), sulpiride (5 or 10 micrograms/microliters), or vehicle (Krebs-Ringer). Locomotor activity was not changed by injection of any drug. However, intrahippocampal injections of scopolamine (9 micrograms/microliters) and sulpiride (10 micrograms/microliters) impaired avoidance behavior, particularly during the last five trials of the task. We conclude that muscarinic-cholinergic and D2-dopaminergic, but not beta-adrenergic or H2-histaminergic, mechanisms in the hippocampus are involved in the performance of one-way active avoidance behavior.

The cholinergic and dopaminergic systems of the prelimbic sector of frontal cortex and memory in the rat.

Rats were trained to perform delayed non-matching to sample (a working/representational memory task) and visual discrimination (a reference/dispositional memory task) in a T-maze, and implanted bilaterally with cannulae in the prelimbic cortex. The rats were tested postoperatively after bilateral 1-microliter injections of vehicle (Krebs-Ringer), sulpiride (10 micrograms/microliter) or scopolamine (18 micrograms/microliter). Sulpiride had no effect on the performance of either task, whereas scopolamine interfered only with the performance of delayed non-matching to sample. We conclude that dopaminergic mechanisms in the prelimbic cortex are not involved in either type of memory and that cholinergic, but not dopaminergic, mechanisms are important for working/representational memory processes.

Continuous and discrete T-maze alternation in rats: effects of intertrial and interrun intervals.

1. Recent concepts concerning animal memory have emphasized the kind of information processed in memory. Reference memory provides information relevant over several trials, i.e., it codes expectancy-based information. Working memory provides information critical for only one trial, i.e., it codes data-based information. Some investigators consider that a continuous alternation task in a T-maze depends on the reference memory of a series of left-right responses, whereas a discrete alternation task is thought to depend on working memory. 2. In the present report, we tested rats in a continuous alternation task with different intertrial intervals (ITI's). Rats were first subjected to 10 or 12 sessions at each of the following ITI's: 0, 55, 100, 200 and 600 s, and then tested at varying ITI's within each session for 12 sessions in the following sequence: 0, 55, 100, 200, 600 and 0 s. Next, the same rats were trained to perform discrete alternation with ITI's and interrun intervals (IRI's) varying across sessions but only IRI's changing within sessions, i.e., IRI = 0 or 55 with ITI = 0, 55, 100, 200 or 600 s across sessions, and IRI = 0, 55, 100, 200 and 600 s with ITI = 0 within sessions. 3. Rats performed both alternation tasks at high levels when ITI's and IRI's changed across sessions. However, when intervals changed within sessions, rats showed a better performance in the continuous task at intervals of 55, 100 and 200 s compared to their performance at these same intervals in the discrete task. In addition, for the discrete task with IRI's changing within sessions, errors probably due to proactive interference occurred more frequently with progressively increasing IRI's. 4. The hypothesis that performance of continuous alternation depends on reference memory and performance of discrete alternation depends on working memory is supported by these data.

Locomotor activity and one-way active avoidance after intrahyppocampal injection of neurotransmitter antagonists

Sixty-three rats with previous training in a T-maze, bilaterally implanted with cannulae directed toward the dorsal hippocampus, were used in this study. All rats received bilateral 1-microngl injections 20 min before testing for locomotor activity (day 1) and one-way active avoidance (day 3). The following drugs were injected into groups of 4 to 8 animals: scopolamine (9 or 18 microng/micronl), propranolol (5 or 10 microng/micronl), cimetidine (0.75 or 1.5 microng/micronl), sulpiride (5 or 10 microng/micronl), or vehicle (Krebs-ringer). Locomotor activity was not changed by injection of any drug. However, intrahippocampal injections of scolpolamine (9 microng/micronl) and sulpiride (10 microng/micronl) impoaired avoidance bahavior, particularly during the last five trials of the task. We conclude that muscarinic-cholinergic and D2-dopaminergic, but not beta-adrenergic or H2-histaminergic, mechanisms in the hippocampus are involved in the performance of one-way active avoidance behavior

The cholinergic and dopaminergic systems of the prelimbic sector of frontal cortex and memory in the rat

Rats were trained to perform delayed non-matching to sample (a working/representational memory task) and visual discrimination(a reference/dispositional memory task) in a T-maze, and implanted bilaterally with cannulae in the prelimbic cortex. The rats were tested postoperatively after bilateral 1 - micronl injections of vehicle (Krebs-Ringer), sulpiride (10 microng/micronl) or scopolamine (18 microng/micronl). Sulpiride had no effect on the performance of either task, whereas scopolamine interfered only with the performance of delayed non-matching to sample. We conclude that dopaminergic mechanisms in the prelimbic cortex are not involved in either type of memory and that cholinergic, but not dopaminergic, mechanisms are important for working/representational memory process