Woody cover and hominin environments in the past 6 million years.

The role of African savannahs in the evolution of early hominins has been debated for nearly a century. Resolution of this issue has been hindered by difficulty in quantifying the fraction of woody cover in the fossil record. Here we show that the fraction of woody cover in tropical ecosystems can be quantified using stable carbon isotopes in soils. Furthermore, we use fossil soils from hominin sites in the Awash and Omo-Turkana basins in eastern Africa to reconstruct the fraction of woody cover since the Late Miocene epoch (about 7 million years ago). (13)C/(12)C ratio data from 1,300 palaeosols at or adjacent to hominin sites dating to at least 6 million years ago show that woody cover was predominantly less than ∼40% at most sites. These data point to the prevalence of open environments at the majority of hominin fossil sites in eastern Africa over the past 6 million years.

Transcranial magnetic stimulation (TMS) in the treatment of attention-deficit/hyperactivity disorder in adolescents and young adults: a pilot study.

OBJECTIVE: Transcranial magnetic stimulation (TMS) uses a medical device that applies magnetic pulses noninvasively to the cortex of the brain to depolarize neurons. We tested its safety and efficacy in young persons with a diagnosis of attention-deficit/hyperactivity disorder (ADHD). METHODS: Transcranial magnetic stimulation was applied to the right prefrontal cortex at 10 Hz, at 100% of the observed motor threshold, for 2000 pulses per session, in a 10-session course over 2 weeks in a sham-controlled crossover design (n=9). There was 1 week of no TMS between the active and sham phases. Safety of TMS was assessed by means of serial audiometry, neuropsychological testing, and electroencephalogram (EEG) at baseline, midpoint, and end point of the study. Efficacy was assessed as a primary outcome by changes in the Clinical Global Impression-Improvement (CGI-I) scale and secondarily by change in the ADHD-IV scale. RESULTS: Transcranial magnetic stimulation was found to be safe, with no serious adverse events and no discontinuations due to adverse effects. All randomized subjects completed the full course of sessions. There were no significant changes in auditory thresholds or in electroencephalographic assessments. Neuropsychological testing showed no significant differences between active and sham groups. There was an overall significant improvement in the clinical global impression of improvement and the ADHD-IV scales across the study phases (active and sham TMS combined; P<0.01), but the change between active and sham TMS phases did not differ. CONCLUSION: Transcranial magnetic stimulation was found to be safe, with no serious adverse events observed in this pilot study. Improvement in symptoms was observed across the combined phases of the study, although there was no difference between the active and sham forms of TMS. Effects of clinical importance should be further assessed in larger controlled studies.