Distracters impair and create working memory-related neuronal activity in the prefrontal cortex.

The prefrontal cortex (PFC) has a central role in working memory (WM). Resistance to distraction is considered a fundamental feature of WM and PFC neuronal activity. However, although unexpected stimuli often disrupt our work, little is known about the underlying neuronal mechanisms involved. In the present study, we investigated whether irregularly presented distracters disrupt WM task performance and underlying neuronal activity. We recorded single neuron activity in the PFC of 2 monkeys performing WM tasks and investigated effects of auditory and visual distracters on WM performance and neuronal activity. Distracters impaired memory task performance and affected PFC neuronal activity. Distraction that was of the same sensory modality as the memorandum was more likely to impair WM performance and interfere with memory-related neuronal activity than information that was of a different sensory modality. The study also shows that neurons not involved in memory processing in less demanding conditions may become engaged in WM processing in more demanding conditions. The study demonstrates that WM performance and underlying neuronal activity are vulnerable to irregular distracters and suggests that the PFC has mechanisms that help to compensate for disruptive effects of external distracters.

A potential aphrodisiac for female macaques.

Earlier studies suggest that alpha2-adrenoceptor antagonists and dopamine receptor agonists may enhance sexual activity in human and nonhuman male primates. It is not known whether these compounds influence the sexual behavior of female primates. We determined whether the administration of a selective alpha2-adrenoceptor antagonist (atipamezole), a dopamine receptor agonist (apomorphine), or their combination to female Macaca arctoides (stumptail macaque) monkeys produces changes in sexual behavior of the female with a male. Following the administration of drugs to the female, the behavior of the female with a male stumptail was observed for 30 min. Atipamezole dose dependently (0.03-0.3 mg/kg im) increased short-time mounting behavior of the male and the total number of copulations. Apomorphine alone (0.125-0.25 mg/kg) or in combination with atipamezole had no significant effects on sexual behavior. The result indicates that a selective alpha2-adrenoceptor antagonist administered in the female stumptail increases sexual behavior of the male with the female. A plausible explanation for this finding is that a selective alpha2-adrenoceptor antagonist increases sexual arousal in female stumptails and this, possibly due to a change in psychosocial behavior of the female, triggers increased sexual activity in males.

Shared means and meanings in vocal expression of man and macaque.

Vocalisations of six Macaca arctoides that were categorised according to their social context and judgements of naive human listeners as expressions of plea/submission, anger, fear, dominance, contentment and emotional neutrality, were compared with vowel samples extracted from simulations of emotional-motivational connotations by the Finnish name Saara and English name Sarah. The words were spoken by seven Finnish and 13 English women. Humans and monkeys resembled each other in the following respects. 'Neutral', 'pleading' and 'commanding' had a similar F0 level. Loud vocalisations of intense 'anger' and 'fear' had both high F0, and the highest values were encountered for 'fear'. Compared with 'neutral', the audiosignal waveform of 'plea/submission' was more sinusoidal, seen in the spectrum as an attenuation of formants and an emphasis of the fundamental, whereas the signal waveform of 'commanding' was more complex corresponding to an increase in noise and a wider distribution of spectral energy. 'Frightened' samples included rather harmonic segments with emphasis of the fundamental, and 'angry' samples included more noise at the low end of the spectrum and often segments with low-frequency ( < 100 Hz) edged modulation. Sounds resembling soft and noisy 'content' grunts of the monkey do not appear in Finnish or English speech but 'content' utterances were, however, associated with low speech pressure, attenuation of harmonics and increase in noise.

Processing of auditory and visual location information in the monkey prefrontal cortex.

Visuospatial working memory mechanisms have been studied extensively at single cell level in the dorsolateral prefrontal cortex (PFCd) in nonhuman primates. Despite the importance of short-term memory of sound location for behavioral orientation, there are only a few studies on auditory spatial working memory. The purpose of this study was to investigate neuronal mechanisms underlying working memory processing of auditory and visual location information at single cell level in the PFCd. Neuronal activity was recorded in monkeys performing a delayed matching-to-sample task (DMTS). The location of a visual or auditory stimulus was used as a memorandum. The majority of the neurons that were activated during presentation of the cue memorandum were selective either for visual or auditory spatial information. A small group of cue related bimodal neurons were sensitive to the location of the cue regardless of whether the stimulus was visual or auditory, suggesting modality independent processing of spatial information at cellular level in the PFCd. Most neurons that were activated during the delay period were modality specific, responding either during visual or auditory trials. All bimodal delay related neurons that responded during both visual and auditory trials were spatially nonselective. The results of the present study suggest that in addition to the modality specific parallel mechanism, working memory of auditory and visual space also involves modality independent processing at cellular level in the PFCd.