Why Do We Step on the Same Rake? The Occurrence of Recurring Errors in the Learning Process

The present study investigated the occurrence of recurring errors in the learning process. Our goal was to determine the reasons for recurring errors. In considering these reasons we were trying to find the characteristic features of incorrect responses at the beginning of a learning process in order to predict the occurrence of recurring errors in the learning process. Response times and confidence measures were used as the predictors of error repetition. The results of two experiments have shown that response times and confidence levels for the recurring and singular errors at the beginning of learning are different. Response times were shorter for recurring errors than for singular errors at the beginning of a learning process. This information can be used to predict the repetition of such errors further along during learning. In addition, in both experiments, the correct responses were slower for stimuli that would cause recurring errors in the future. This allowed us to predict the repetition of such errors. Participants’ confidence estimates also varied with different types of erroneous responses and allowed the repetition of errors during the learning process to be predicted. Thus, our results allow the prediction of error repetition and also can be used to make suggestions about the phenomenon of recurring errors and the causes of their occurrence.

Signaling incentive and drive in the primate ventral pallidum for motivational control of goal-directed action

Processing incentive and drive is essential for control of goal-directed behavior. The limbic part of the basal ganglia has been emphasized in these processes, yet the exact neuronal mechanism has remained elusive. In this study, we examined the neuronal activity of the ventral pallidum (VP) and its upstream area, the rostromedial caudate (rmCD), while two male macaque monkeys performed an instrumental lever-release task, in which a visual cue indicated the forthcoming reward size. We found that the activity of some neurons in VP and rmCD reflected the expected reward-size transiently following the cue. Reward-size coding appeared earlier and stronger in VP than in rmCD. We also found that the activity in these areas was modulated by the satiation level of monkeys, which also occurred more frequently in VP than in rmCD. The information regarding reward-size and satiation-level was independently signaled in the neuronal populations of these areas. The data thus highlighted the neuronal coding of key variables for goal-directed behavior in VP. Furthermore, pharmacological inactivation of VP induced more severe deficit of goal-directed behavior than inactivation of rmCD, which was indicated by abnormal error repetition and diminished satiation effect on the performance. These results suggest that VP encodes incentive value and internal drive, and plays a pivotal role in the control of motivation to promote goal-directed behavior.Significance StatementThe limbic part of the basal ganglia has been emphasized in the motivational control of goal-directed action. Here, we investigated how the ventral pallidum (VP) and the rostromedial caudate (rmCD) encode incentive value and internal drive, and control goal-directed behavior. Neuronal recording and subsequent pharmacological inactivation revealed that VP had stronger coding of reward size and satiation level than rmCD. Reward size and satiation level were independently encoded in the neuronal population of these areas. Furthermore, VP inactivation impaired goal-directed behavior more severely than rmCD inactivation. These results highlighted the central role of VP in the motivational control of goal-directed action.

Analysis of error type and frequency in apraxia of speech among Portuguese speakers

Most studies characterizing errors in the speech of patients with apraxia involve English language. Objectives: To analyze the types and frequency of errors produced by patients with apraxia of speech whose mother tongue was Brazilian Portuguese. Methods: 20 adults with apraxia of speech caused by stroke were assessed. The types of error committed by patients were analyzed both quantitatively and qualitatively, and frequencies compared. Results: We observed the presence of substitution, omission, trial-and-error, repetition, self-correction, anticipation, addition, reiteration and metathesis, in descending order of frequency, respectively. Omission type errors were one of the most commonly occurring whereas addition errors were infrequent. These findings differed to those reported in English speaking patients, probably owing to differences in the methodologies used for classifying error types; the inclusion of speakers with apraxia secondary to aphasia; and the difference in the structure of Portuguese language to English in terms of syllable onset complexity and effect on motor control. Conclusions: The frequency of omission and addition errors observed differed to the frequency reported for speakers of English.