Extraversion has two central characteristics: (1) interpersonal engagement, which consists of affiliation (enjoying and valuing close interpersonal bonds, being warm and affectionate) and agency (being socially dominant, enjoying leadership roles, being assertive, being exhibitionistic, and having a sense of potency in accomplishing goals) and (2) impulsivity, which emerges from the interaction of extraversion and a second, independent trait (constraint). Agency is a more general motivational disposition that includes dominance, ambition, mastery, efficacy, and achievement. Positive affect (a combination of positive feelings and motivation) is closely associated with extraversion. Extraversion is accordingly based on positive incentive motivation. Parallels between extraversion (particularly its agency component) and a mammalian behavioral approach system based on positive incentive motivation implicate a neuroanatomical network and modulatory neurotransmitters in the processing of incentive motivation. A corticolimbic-striatal-thalamic network (1) integrates the salient incentive context in the medial orbital cortex, amygdala, and hippocampus; (2) encodes the intensity of incentive stimuli in a motive circuit composed of the nucleus accumbens, ventral pallidum, and ventral tegmental area dopamine projection system; and (3) creates an incentive motivational state that can be transmitted to the motor system. Individual differences in the functioning of this network arise from functional variation in the ventral tegmental area dopamine projections, which are directly involved in coding the intensity of incentive motivation. The animal evidence suggests that there are three neurodevelopmental sources of individual differences in dopamine: genetic, "experience-expectant," and "experience-dependent." Individual differences in dopamine promote variation in the heterosynaptic plasticity that enhances the connection between incentive context and incentive motivation and behavior. Our psychobiological threshold model explains the effects of individual differences in dopamine transmission on behavior, and their relation to personality traits is discussed.

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Neurobiology of the structure of personality: Dopamine, facilitation of incentive motivation, and extraversion.

Time is a fundamental dimension of life. It is crucial for decisions about quantity, speed of movement and rate of return, as well as for motor control in walking, speech, playing or appreciating music, and participating in sports. Traditionally, the way in which time is perceived, represented and estimated has been explained using a pacemaker-accumulator model that is not only straightforward, but also surprisingly powerful in explaining behavioural and biological data. However, recent advances have challenged this traditional view. It is now proposed that the brain represents time in a distributed manner and tells the time by detecting the coincidental activation of different neural populations.

/pdf/what-makes-us-tick-functional-and-neural-mechanisms-of-4ldejchzsz.pdf

What makes us tick? Functional and neural mechanisms of interval timing

Neuropharmacology of timing and time perception.

A complete understanding of sensory and motor processing requires characterization of how the nervous system processes time in the range of tens to hundreds of milliseconds (ms). Temporal processing on this scale is required for simple sensory problems, such as interval, duration, and motion discrimination, as well as complex forms of sensory processing, such as speech recognition. Timing is also required for a wide range of motor tasks from eyelid conditioning to playing the piano. Here we review the behavioral, electrophysiological, and theoretical literature on the neural basis of temporal processing. These data suggest that temporal processing is likely to be distributed among different structures, rather than relying on a centralized timing area, as has been suggested in internal clock models. We also discuss whether temporal processing relies on specialized neural mechanisms, which perform temporal computations independent of spatial ones. We suggest that, given the intricate link between temporal and spatial information in most sensory and motor tasks, timing and spatial processing are intrinsic properties of neural function, and specialized timing mechanisms such as delay lines, oscillators, or a spectrum of different time constants are not required. Rather temporal processing may rely on state-dependent changes in network dynamics.

/pdf/the-neural-basis-of-temporal-processing-3u6cgcgz99.pdf

The neural basis of temporal processing

http://prism.bham.ac.uk/pdf_files/lewis_miall_03.pdf

Distinct systems for automatic and cognitively controlled time measurement: evidence from neuroimaging.

Adult subjects were presented with two auditory stimuli per trial, and their task was to decide which of the two was longer in duration. An adaptive psychophysical procedure was used. In Experiments 1, 2, and 4, the base duration was 50 msec, whereas in Experiment 3, the base duration was 1 sec. In Experiments 1, 2, and 4, it was found that filled intervals (continuous tones) were discriminated more accurately than empty intervals (with onset and offset marked by clicks). It was concluded that this difference was perceptual rather than cognitive in nature, since performance on filled and empty intervals was not affected by increasing cognitive load in a dual-task procedure (Experiment 2) but was affected by backward masking (Experiment 4). In contrast, the results of Experiment 3 showed that duration discrimination of filled auditory intervals of longer duration was cognitively influenced, since performance was impaired by increasing cognitive load. Implications for notions of perceptual processing and timing mechanisms tanderlying differences in duration discrimination with filled and empty intervals are discussed.

/pdf/duration-discrimination-of-filled-and-empty-auditory-3vh7nreqp0.pdf

Duration discrimination of filled and empty auditory intervals: Cognitive and perceptual factors

On dopaminergic modulation of temporal information processing.

There is some experimental evidence suggesting that temporal processing of brief duration in the range of milliseconds is based on dopamine (DA)-dependent neural counting mechanisms, whereas processin

Are There Dissociable Roles of the Mesostriatal and Mesolimbocortical Dopamine Systems on Temporal Information Processing in Humans

Recent findings suggest that temporal processing of brief durations is a function of dopaminergic neurotransmission in the basal ganglia. Furthermore, there is preliminary evidence of abnormal timing functions in patients suffering from idiopathic Parkinson's disease (PD). In the present study, temporal discrimination of intervals in the range of milliseconds was investigated in 20 PD patients and 20 healthy controls matched for sex and age. Temporal discrimination was significantly impaired in PD patients as compared to healthy controls. For PD patients, additional correlational analyses did not yield any significant relationship between performance on temporal processing and degree of motor impairment or illness duration. However, impairment in temporal processing was associated with dosage of L-DOPA substitution and self-rated feelings of depression. The overall pattern of results suggests that deficits in temporal information processing observed in PD patients may represent a trait marker of vulnerabi...

Impaired Temporal Discrimination in Parkinson's Disease: Temporal Processing of Brief Durations as an Indicator of Degeneration of Dopaminergic Neurons in the Basal Ganglia

Performance in temporal discrimination of time intervals in the range of milliseconds was compared in 80 healthy subjects, 27 patients with schizophrenic disorders, 33 patients with major depression, 21 patients with dysthymic disorders. For schizophrenic patients as well as for patients with major depression, pronounced deficits in duration discrimination could be demonstrated as compared to the healthy control group (p <. 01). Patients with dysthymic disorders and schizophrenic patients differed significantly from the melancholic group (p <. 01 and p <. 05, respectively). The results are discussed on the basis of the assumption of an internal clock, implying that the clock rate is highest and therefore temporal resolution is best with healthy subjects. With psychiatric patients performance in temporal discrimination was impaired to a slowing down in clock rate and thus decreased temporal resolution. There is strong evidence that changes in clock rate depend on the effective level of dopamine. This leads...

Thomas Rammsayer

Papers

Duration discrimination of filled and empty auditory intervals: Cognitive and perceptual factors

On dopaminergic modulation of temporal information processing.

Are There Dissociable Roles of the Mesostriatal and Mesolimbocortical Dopamine Systems on Temporal Information Processing in Humans

Impaired Temporal Discrimination in Parkinson's Disease: Temporal Processing of Brief Durations as an Indicator of Degeneration of Dopaminergic Neurons in the Basal Ganglia

Temporal discrimination in schizophrenic and affective disorders: evidence for a dopamine-dependent internal clock.