parts

Louis J. Sheehan

Scientists have uncovered a new brain difference between right-handers and left-handers. For righties, a region near the back of the left brain fosters the capacity to focus on distinguishable parts of an object rather than on the whole entity, as previous research indicated. For lefties, a corresponding right brain area promotes the same capacity to see the proverbial trees while ignoring the forest, according to a team led by Carmel Mevorach of the University of Birmingham in England.http://ljsheehan.livejournal.com

The scientists probed 11 right-handed and 11 left-handed adults using transcranial magnetic stimulation (TMS). Each volunteer sat under a coil that delivered low-intensity magnetic pulses through the skull to either of the corresponding brain areas, temporarily disrupting neural activity there. Participants used a computer to view a series of letters and shapes composed of smaller parts, such as a large letter H composed of 10 small letter Ds. Before and after a bout of magnetic stimulation, the volunteers were asked to identify as fast they could on the computer display either parts of an object or the whole object.http://louis-j-sheehan.info

The time required to identify parts of objects increased markedly when the scientists briefly disabled either the key left-brain region in right-handers or the equivalent right-brain region in left-handers.

brief

Around 36,000 years ago, Neandertals and people lived side by side in southwestern France for at least a millennium, according to a newly assembled chronology of ancient occupations there. Paul Mellars of Cambridge University in England and his coworkers say that their work supports the controversial view that shortly before dying out about 28,000 years ago, Neandertals borrowed toolmaking techniques from neighboring Homo sapiens.http://www.myspace.com/louis_j_sheehan_esquire

Mellars' team took radiocarbon measurements to date animal bones previously excavated at a French cave. Neandertal stone tools recovered there, dubbed Chatelperronian artifacts, display a toolmaking style that blends techniques typical of Neandertals and of Late Stone Age people.

From the ages of bones found with various tools, the scientists conclude that two periods of Chatelperronian toolmaking occurred in the cave, one 40,000 to 39,000 years ago and the second between 36,000 and 34,500 years ago. Implements with sharpened edges characteristic of human toolmaking were also unearthed in the cave and date to between 39,000 and 36,000 years ago, the scientists report in the Nov. 3 Nature.

The Neandertal occupations of the cave coincided with relatively warm eras that sandwiched a colder period during which modern humans moved in, Mellars says. The artifact record shows an overlap of the two species in the cave around 36,000 years ago, though the two groups might not actually have used the cave simultaneously.http://www.myspace.com/louis_j_sheehan_esquire

It was during such brief periods of coexistence between the two species in southwestern Europe that Neandertals adopted some modern toolmaking techniques, Mellars argues.

It's more likely that Neandertals developed Chatelperronian tools on their own and never abandoned the French site, counters João Zilhão of Cidade University in Lisbon, Portugal. The cave studied by Mellars contained only a few humanmade tools that are probably about 36,000 years old, reflecting no more than a brief incursion, Zilhão says.