1. This study was devoted to the neuronal processes underlying the construction of the motor program. Two monkeys were trained in a choice reaction time task to perform precise wrist flexion and extension movements of small and large extent. During a trial, the first visual signal, the preparatory signal (PS), informed the animal completely, partially, or not at all about direction and/or extent of the forthcoming movement. After a constant waiting period, a second visual signal, the response signal (RS), was illuminated calling for execution of the requested movement. 2. Reaction time (RT) and movement time (MT) measurements during the training as well as the recording sessions revealed that providing prior information about movement parameters strongly affected RT, but only slightly affected MT. Reaction time decreased in relation to the amount (number of movement parameters precued) and the type of prior information. Providing information about movement direction shortened RT much more than providing information about movement extent. Behavioral data support a parametric conception of motor programming, i.e., that the programming of the different movement parameters results from assembling separate processes of different duration. These results are compatible with the model in which programming processes are serially and hierachically ordered, movement direction being processed before movement extent. 3. Single-cell recording techniques were used to study neuronal activity of the primary motor (MI) and the premotor (PM) cortex, contralateral to the active arm. The activity of 155 neurons of MI and 158 neurons of PM was recorded during performance of the task. Of these 313 neurons, only 14 neurons did not change their activity during execution of the task. Two hundred and seven neurons whose activity changes were related to movement direction and/or movement extent have been selected for the further study. They were classified into three main groups: 1) execution-related neurons (49 in MI, 27 in PM), 2) preparation- and execution-related neurons (48 in MI, 54 in PM), and 3) preparation-related neurons (8 in MI, 21 in PM). 4. Directionally selective, execution-related neurons were found to be more frequently located within MI (81/105, 77.1%) than within PM (55/102, 53.9%), whereas directionally selective, preparation-related neurons appeared to be more frequently located within PM (47/102, 46.1%) than within MI (24/105, 22.9%).(ABSTRACT TRUNCATED AT 400 WORDS)

The effects of Simon-and Stroop-like stimuli are examined in isolation and in factorial combinations with different delays between the presentation of the irrelevant and the relevant stimuli. The effects of irrelevant stimuli have different time courses depending on whether they overlap with the relevant stimulus (stimulus-stimulus overlap, Dimensional Overlap [DO] Type 4) or with the response (stimulus-response overlap, DO Type 3). A new, computational, parallel distributed processing (PDP)-type model, DO'97, is presented that is based on the original DO model (S. Kornblum, 1994;S. Kornblum, T. Hasbroucq, & A. Osman, 1990), and it postulates a nonmonotone irrelevant stimulus activation function in addition to 2 temporally ordered, serial, nonindependent stages: a stimulus processing stage and a response production stage. DO'97 is able to simulate the temporal dynamic characteristics of the processes, with good fits to the empirical data of this study and other published studies, at the level of means, variances, and distributional plots.After decades of empirical, and generally fragmented, research on stimulus-stimulus (S-S) and stimulus-response (S-R) compatibility effects, attempts have recently been made to understand the broad theoretical underpinnings of this large class of phenomena. Some of these attempts, instead of treating each effect in isolation, as had been done in the past, have tried to identify the processing principles that they have in common. Thus, by carefully examining these effects, particularly the effects of irrelevant stimuli, many similarities have become apparent. For example, when the irrelevant aspects of a stimulus are consistent with the relevant aspects either of the stimulus or of the response, reaction times (RTs) tend to be faster than when they are inconsistent (for reviews see Prinz, 1997, andProctor &Reeve, 1990). 1 Different combinations of such consistency relationships produce the so-called Stroop effect (for a review see MacLeod, 1991), the Simon effect (for a review see Simon, 1990), and other compatibility effects.

Why is vocal music the oldest and still the most popular form of music? Very possibly because vocal music involves an intimate combination of speech and music, two of the most specific, high-level skills of human beings. The issue we address is whether people listening to a song treat the linguistic and musical components separately or integrate them within a single percept. Event-related potentials were recorded while musicians listened to excerpts from operas sung a capella. Excerpts were ended by semantically congruous or incongruous words sung either in or out of key. Results clearly demonstrated the independence of lyrics and tunes, so that an additive model of semantic-and harmonic-violations processing predicted the data extremely well. These results are consistent with a modular organization of the human cognitive system and open new perspectives in the search for the similarities and differences between language and music processing.

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