It has been empirically established that the cerebral cortical areas defined by Brodmann one hundred years ago solely on the basis of cellular organization are closely correlated to their function, such as sensation, association, and motion. Cytoarchitectonically distinct cortical areas have different densities and types of neurons. Thus, signaling patterns may also vary among cytoarchitectonically unique cortical areas. To examine how neuronal signaling patterns are related to innate cortical functions, we detected intrinsic features of cortical firing by devising a metric that efficiently isolates non-Poisson irregular characteristics, independent of spike rate fluctuations that are caused extrinsically by ever-changing behavioral conditions. Using the new metric, we analyzed spike trains from over 1,000 neurons in 15 cortical areas sampled by eight independent neurophysiological laboratories. Analysis of firing-pattern dissimilarities across cortical areas revealed a gradient of firing regularity that corresponded closely to the functional category of the cortical area; neuronal spiking patterns are regular in motor areas, random in the visual areas, and bursty in the prefrontal area. Thus, signaling patterns may play an important role in function-specific cerebral cortical computation.

1. Neuronal activity was recorded from the premotor cortex (PM) of Japanese monkeys while they performed hand movements with different amplitudes and directions. On each behavioral trial, two instructions were given sequentially: 1) an amplitude instruction (large or small) and 2) a direction instruction (flexion or extension). The onset of movement was triggered by a visual signal after a delay period. 2. Among various kinds of task-related neuronal activity recorded in the PM, two types were selected for study: 1) set-related activity, sustained activity change during the delay period that followed presentation of instruction signals (IS); and 2) movement-related activity, activity change immediately before and during movement, which followed the trigger signal (TS) presentation. 3. Thirty-two of 101 set-related neurons showed activity change after presentation of the first IS (Delay 1 set-related activity), when they were instructed in either amplitude or direction, but not both. All of the set-related neurons showed activity modulation after presentation of the second IS (Delay 2 set-related activity). When neurons showed both Delay 1 and Delay 2 set-related activity, they were usually more active during Delay 2, i.e., when the monkeys had received both amplitude and directional ISs. A majority of neurons with Delay 2 set-related activity (64%) showed relation to both movement amplitude and direction. Twenty-eight percent of the neurons showed relation to either amplitude or direction, but not both. These findings seem consistent with a view that serial, rather than parallel, processes of motor programming operate in preparation of intended movements. 4. A majority of PM neurons with movement-related activity (51%) showed activity change related to both the direction and amplitude of movement. Forty-two percent showed selective relation to either direction or amplitude. These findings support a view that PM contributes to the control of limb movements. 5. Histological reconstruction showed that a vast majority of PM set-related neurons were located in the dorsal aspect of the PM (PMd), medial to the arcuate spur and lateral to the superior precentral sulcus. In contrast, movement-related neurons were distributed in two distinct foci: one in the ventral aspect of the PM (PMv), immediately caudal to the genu of the arcuate sulcus and lateral to the spur of the sulcus; and the other in the PMd, overlap;ing the location of set-related neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Measurement of stress hormones is a common objective method for assessment of mental stress. However, the stress of blood sampling alone may also increase stress hormone levels. In the present study, we sampled salivary biomarkers from healthy volunteers under noninvasive conditions and determined their efficacy to assess mental stress. Specifically, we examined the relationship between State Anxiety Inventory score (STAI-s) in subjects exposed to arithmetic stress and salivary chromogranin-A, alpha-amylase, or cortisol. The STAI-s was significantly correlated to salivary alpha-amylase (r = 0.589; P < 0.01) but not to salivary chromogranin-A or cortisol. Therefore, salivary alpha-amylase is a useful indicator of psychosocial stress.

1. A gamma aminobutyric acid (GABAA) receptor agonist, muscimol (Sigma, 5 micrograms/microliters solution), and a GABAB receptor agonist and antagonist, baclofen and phaclofen, respectively, were injected (1.0 microliter) into the dorsal and ventral aspects of the premotor cortex (PM) of two Japanese monkeys (Macaca fuscata), while they were performing a motor task that required wrist flexion or extension to a target. The correct movement was instructed by either 1) a conditional color cue [green or red light emitting diodes (LED)] equidistant from the targets or 2) a directional cue toward extension or flexion (right or left LED). When the green or right LED was illuminated, extension was to be performed. When the red or left LED was illuminated, flexion was required. The movement was triggered by a visual stimulus either simultaneously with the instruction stimulus or after a variable delay. 2. Before drug injection, single-unit recordings were made to select injection sites 1) in the dorsal aspect of the PM (PMd) around the superior precentral sulcus where typical set-related activity was frequently recorded and 2) in the ventral aspect of the PM (PMv) immediately caudal to the genu of the arcuate sulcus where movement-related neurons were densely located. 3. Behavioral deficits were observed primarily at the time muscimol, but not baclofen or phaclofen, was injected. Furthermore, muscimol effects were short-lasting: deficits were most frequently observed during the 10-min injection period but seldom after completion of injection. 4. When muscimol was injected into the PMd, there was an increase in the number of direction errors primarily when the conditional cues were presented. The initiated movements were similar in amplitude and velocity to the preinjection behavior. In contrast, when muscimol was injected into the PMv, many of the initiated movements showed smaller amplitudes and slower velocities, but few direction errors were made. 5. These results suggest that the PMd and PMv play differential roles in motor control: the PMd is more important than PMv in conditional motor behavior and plays a role in the preparation for forthcoming movements. In contrast, the PMv is more specialized for a role in the execution of visually guided movements.

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