Functional Differences in the Backward Shifts of CA1 and CA3 Place Fields in Novel and Familiar Environments

Insight into the processing dynamics and other neurophysiological properties of different hippocampal subfields is critically important for understanding hippocampal function. In this study, we compared shifts in the center of mass (COM) of CA3 and CA1 place fields in a familiar and completely novel environment. Place fields in CA1 and CA3 were simultaneously recorded as rats ran along a closed loop track in a familiar room followed by a session in a completely novel room. This process was repeated each day over a 4-day period. CA3 place fields shifted backward (opposite to the direction of motion of the rat) only in novel environments. This backward shift gradually diminished across days, as the novel environment became more familiar with repeated exposures. Conversely, CA1 place fields shifted backward across all days in both familiar and novel environments. Prior studies demonstrated that CA1 place fields on average do not exhibit a backward shift during the first exposure to an environment in which the familiar cues are rearranged into a novel configuration, although CA3 place fields showed a strong backward shift. Under the completely novel conditions of the present study, no dissociation was observed between CA3 and CA1 during the first novel session (although a strong dissociation was observed in the familiar sessions and the later novel sessions). In summary, this is the first study to use simultaneous recordings in CA1 and CA3 to compare place field COM shift and other associated properties in truly novel and familiar environments. This study further demonstrates functional differentiation between CA1 and CA3 as the plasticity of CA1 place fields is affected differently by exposure to a completely novel environment in comparison to an altered, familiar environment, whereas the plasticity of CA3 place fields is affected similarly during both types of environmental novelty

Comparison of acute toxicities of two chemotherapy schedules for head and neck cancers

Background: Chemo-radiotherapy has become the standard of care for loco-regionally advanced head and neck cancers. Platinum based regimens are the most effective. Although benefits are proven with chemo-radiation, acute toxicities are markedly increased. The dose and delivery schedules of Cisplatin have ranged from intermittent higher dose [100 mg/m2] every 3 weeks to low dose [6 mg/m2] daily administration. At present there is no data indicating which regimen is superior. Purpose: To compare acute toxicities of two chemotherapy schedules for head and neck cancers. Materials and Methods: A total of 83 head and neck cancer patients treated with two schedules of concurrent chemo RT were analyzed, retrospectively, for treatment toxicity. In group A [51 patients], chemotherapy [CT] was administered on week 1, 4 and 7 [cisplatin 100 mg/m2] over a period of 2-3 days. In group B [32 patients], CT was delivered weekly [cisplatin 40 mg/m2]. Radiotherapy dose was 7000 cGy in 35 fractions for definitive concurrent chemo-radiation and 6600 cGy in 33 fractions for adjuvant treatment. Results: Group B patients had increased grade III skin and hematological toxicity, where as patients in group A had more pharyngeal toxicity. Treatment interruptions and percentage of weight loss were higher in group B. Weekly CT schedule had higher rate of severe mucositis, which was statistically significant on both univariate [ P =0.005] and multivariate [ P =0.007] analysis. Conclusions: Three weekly CT is less toxic than weekly. Weekly CT can be made more acceptable by reducing the dose and using feeding tubes for nutrition

Comparison of acute toxicities of two chemotherapy schedules for head and neck cancers

International audienc

Comparison of acute toxicities of two chemotherapy schedules for head and neck cancers

Background: Chemo-radiotherapy has become the standard of care for loco-regionally advanced head and neck cancers. Platinum based regimens are the most effective. Although benefits are proven with chemo-radiation, acute toxicities are markedly increased. The dose and delivery schedules of Cisplatin have ranged from intermittent higher dose [100 mg/m2] every 3 weeks to low dose [6 mg/m2] daily administration. At present there is no data indicating which regimen is superior. Purpose: To compare acute toxicities of two chemotherapy schedules for head and neck cancers. Materials and Methods: A total of 83 head and neck cancer patients treated with two schedules of concurrent chemo RT were analyzed, retrospectively, for treatment toxicity. In group A [51 patients], chemotherapy [CT] was administered on week 1, 4 and 7 [cisplatin 100 mg/m2] over a period of 2-3 days. In group B [32 patients], CT was delivered weekly [cisplatin 40 mg/m2]. Radiotherapy dose was 7000 cGy in 35 fractions for definitive concurrent chemo-radiation and 6600 cGy in 33 fractions for adjuvant treatment. Results: Group B patients had increased grade III skin and hematological toxicity, where as patients in group A had more pharyngeal toxicity. Treatment interruptions and percentage of weight loss were higher in group B. Weekly CT schedule had higher rate of severe mucositis, which was statistically significant on both univariate [ P =0.005] and multivariate [ P =0.007] analysis. Conclusions: Three weekly CT is less toxic than weekly. Weekly CT can be made more acceptable by reducing the dose and using feeding tubes for nutrition