Response of multiple simultaneously recorded macaque area LIP neurons in a memory saccade task

Cells in the lateral intraparietal cortex (LIP) of rhesus macaques respond vigorously and in spatially-tuned fashion to briefly memorized visual stimuli. Responses to stimulus presentation, memory maintenance, and task completion are seen, in varying combination from neuron to neuron. To help elucidate this functional segmentation a new system for simultaneous recording from multiple neighboring neurons was developed. The two parts of this dissertation discuss the technical achievements and scientific discoveries, respectively.

Technology. Simultanous recordings from multiple neighboring neurons were made with four-wire bundle electrodes, or tetrodes, which were adapted to the awake behaving primate preparation. Signals from these electrodes were partitionable into a background process with a 1/f-like spectrum and foreground spiking activity spanning 300-6000 Hz. Continuous voltage recordings were sorted into spike trains using a state-of-the-art clustering algorithm, producing a mean of 3 cells per site. The algorithm classified 96% of spikes correctly when tetrode recordings were confirmed with simultaneous intracellular signals. Recording locations were verified with a new technique that creates electrolytic lesions visible in magnetic resonance imaging, eliminating the need for histological processing. In anticipation of future multi-tetrode work, the chronic chamber microdrive, a device for long-term tetrode delivery, was developed.

Science. Simultaneously recorded neighboring LIP neurons were found to have similar preferred targets in the memory saccade paradigm, but dissimilar peristimulus time histograms, PSTH). A majority of neighboring cell pairs had a difference in preferred directions of under 45° while the trial time of maximal response showed a broader distribution, suggesting homogeneity of tuning with het erogeneity of function. A continuum of response characteristics was present, rather than a set of specific response types; however, a mapping experiment suggests this may be because a given cell's PSTH changes shape as well as amplitude through the response field. Spike train autocovariance was tuned over target and changed through trial epoch, suggesting different mechanisms during memory versus background periods. Mean frequency-domain spike-to-spike coherence was concentrated below 50 Hz with a significant maximum of 0.08; mean time-domain coherence had a narrow peak in the range ±10 ms with a significant maximum of 0.03. Time-domain coherence was found to be untuned for short lags (10 ms), but significantly tuned at larger lags (50 ms).

Activity in the pallial nerve of knobbed (Busycon carica) and channeled (Busycotypus canaliculatum) whelks recorded during exposure of the osphradium to odorant solutions

Adult horseshoe crabs (Limulus polyphemus) are the preferred bait in the U.S. east coast whelk pot fishery, but their harvest is being restricted because of severe population declines in the Chesapeake and Delaware bays. To identify other baits, the activity in the pallial nerve of whelks was determined during exposure of the osphradium to odorant solutions prepared from horseshoe crab eggs, horseshoe crab hemolymph, and hard clam (Mercenaria mercenaria) tissue. All three elicited significant responses; bait based on them may provide an alternative to the use of adult horseshoe crabs, although extensive behavioral testing remains to be done. Channeled whelk did not respond to molecular weight fractions (>3 kDa and <3 kDa) prepared from horseshoe crab egg odorant solutions but did respond when the molecular weight fractions were recombined. Whelks appear to have broadly tuned chemoreceptors and manufactured baits may need to mimic the complex mixture of odorants derived from natural sources.

Território de gente e de música: Jovens no Centro cultural Cartola e o cotidiano de uma experiência

Este trabalho busca compor um quadro das práticas cotidianas de jovens frequentadores das oficinas de jazz oferecidas pelo Centro Cultural Cartola (CCC). Contextualizado dentro de um universo tradicionalmente conhecido por sua origem no samba, esse território de arte e de expressão através do corpo e da música contempla outros movimentos musicais, principalmente o jazz e o moderno, possibilitando um conjunto de múltiplos sentidos e ressignificações na vida destes participantes. Como fundamentação epistemológica, foi utilizada a Teoria Ator-Rede (TAR), concebida como forma de abordar a fabricação dos fatos, ao abranger, simetricamente, natureza e sociedade, humano e não humano. Foram igualmente consideradas as possíveis configurações de interação e sociabilidade que envolvem território, sujeito e demais atores da rede, os quais conseguem reconhecer-se diante do outro, do diferente, e construírem um projeto individual e coletivo frente à sociedade multicultural em que estão inseridos. Para isso, foram realizadas entrevistas que, por sua vez, são complementos à descrição interpretativa registrada no diário de campo, permitindo a dimensão de improviso, de manejo das situações e de envolvimento nas incessantes redefinições processuais. O campo explorado foi, estritamente, o de jovens adolescentes, num recorte etário de 14 a 21 anos. Todos deveriam estar matriculados na escola ensino fundamental e médio e residir em comunidade, não sendo necessariamente a Mangueira. As abordagens contemplaram também as incontáveis participações do professor da oficina de jazz. Durante o processo, emanou-se a existência de um apaixonamento e de uma apropriação por parte de todos os envolvidos com a oficina: parte administrativa, pedagógica e docente, garantindo autonomia e diferencial no universo social do grupo, cujas escolhas legitimam o quanto o investimento na cultura produz artistas conscientes da beleza inerente à própria arte e aos afetamentos daí advindos. Interessante ressaltar que o samba funciona como marca histórica e temporal do CCC, mas a principal motivação ali percebida estava no encontro mediado pela dança, junção corpo/música, presente na vida dos participantes desde a infância, além do prazer de pertencerem a um grupo afim, movido por histórias semelhantes. Junto a isso, o professor exercia o papel de liderança velada, a mediar as relações e a produzir efeitos de coesão grupal, com suas ideias e incentivo à expressão pela dança, de modo a dar lugar a novas descobertas e ressignificação

Holocene climate and El Nino history as recorded in the sediments of northern coastal Peru [abstract, table, and references]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The history of the El Nino phenomena is recorded in both the fluvial and coastal sediments of northern Peru. The fluvial record was presented at the 1987 PACLIM Workshop and is discussed in detail elsewhere (Wells, 1987). However, the number of radiocarbon dated El Nino events has increased since Wells (1987) was published; this data is presented in Table 1.

Holocene history of the El Niño phenomenon as recorded in flood sediments of northern coastal Peru

EXTRACT (SEE PDF FOR FULL ABSTRACT): The Holocene history of flooding in northern coastal Peru is believed to be a proxy record for the El Niño phenomenon. A recently completed set of 30 radiocarbon dates on overbank flood deposits and a tsunami deposit from the Casma region (Figure 1 and Table 1) establishes a chronology for the largest events that have occurred during the last 3500 years. ... The data presented here indicate that events much larger than the one in 1982-1983 may occur with a frequency of about once every 1000 years.