Biomedical subjects

Yukari Hashimoto

Publications and source records attributed to Yukari Hashimoto.

3 recordsLinked to original sources

PubMed2005

Learning performance on the discrimination-shift task in patients with cortical and subcortical lesions.

Patients with brain damage completed reversal and nonreversal shift-learning tasks and we compared their performance with that of normal adults. The overall group differences revealed that many patients could not reach the task criterion regardless of the location of damage and the shift condition of the task. When we compared patients with subcortical and cortical damage, we also found no group differences with regard to the total number of trials required to reach the learning criterion and in terms of their learning processes during shift learning. However, when we compared patients with subcortical and unilateral cortical damage, the results revealed that the learning processes of patients with subcortical damage were normal, whereas the patients with unilateral cortical damage showed lesion-specific effects on shift learning. These findings are discussed in light of previous developmental findings and the proposed role of subcortical structures in learning.

Aged↗

PubMed2005

Familiarity effect on retrieval: a neuropsychological case study.

NM, who suffered traumatic brain injury (TBI) to the prefrontal cortex (PFC), was compared with a diffuse axonal injury (DAI) patient on tasks of free recall, cued recall and recognition memory. We manipulated the familiarity of items to explore the effects of item strength on retrieval. On free recall, NM performed best during the high-familiarity picture condition. On cued recall, he performed best during the high-familiarity word condition. Although high familiarity improved his accuracy on picture items in free recall, low familiarity improved his recognition of words. The patient with DAI did not show these patterns. The role of the PFC in memory is discussed in terms of plausible recognition processes.

Adult↗

PubMed2004

In planta functions of the Arabidopsis cytokinin receptor family.

Since their discovery as cell-division factors in plant tissue culture about five decades ago, cytokinins have been hypothesized to play a central role in the regulation of cell division and differentiation in plants. To test this hypothesis in planta, we isolated Arabidopsis plants lacking one, two, or three of the genes encoding a subfamily of histidine kinases (CRE1, AHK2, and AHK3) that function as cytokinin receptors. Seeds were obtained for homozygous plants containing mutations in all seven genotypes, namely single, double, and triple mutants, and the responses of germinated seedlings in various cytokinin assays were compared. Both redundant and specific functions for the three different cytokinin receptors were observed. Plants carrying mutations in all three genes did not show cytokinin responses, including inhibition of root elongation, inhibition of root formation, cell proliferation in and greening of calli, and induction of cytokinin primary-response genes. The triple mutants were small and infertile, with a reduction in meristem size and activity, yet they possessed basic organs: roots, stems, and leaves. These results confirm that cytokinins are a pivotal class of plant growth regulators but provide no evidence that cytokinins are required for the processes of gametogenesis and embryogenesis.

Arabidopsis↗