Reply: Is there evidence of a subordinate role of the hippocampal CA1 field for declarative memory formation?

Sir,Witt and colleagues from the Bonn Epilepsy Centre in Germany reviewed a recent study about differential influence of hippocampal subfields on memory formation in a series of 100 patients with temporal lobe epilepsy (TLE) (Coras et al. , 2014). A previous report from the Bonn group addressed a similar issue (Witt et al. , 2014) but came to different conclusions. This controversy on impact of hippocampal subfields in the anatomical organization of human memory requires a comprehensive discussion, as raised by Witt et al. (2014) in their letter to Brain , but also reflect a long-standing debate resulting from lack of international consensus and diversity of applied neuropsychological memory test protocols in patients with TLE. Thus, any comparison of published results remains difficult.Recent progress in histomorphological analysis of the epileptic human hippocampus identified different lesion patterns, which are now classified according to an international consensus classification for hippocampal sclerosis (Blumcke et al. , 2012, 2013 a , b ). It suggests that hippocampal sclerosis in TLE result from different aetiologies (and clinical histories) rather than representing a single disease. Clinical features support this assumption, i.e. differences in age of epilepsy onset and post-surgical seizure control. Our working group also studied differences in memory performance related to hippocampal sclerosis subtypes using invasive intracarotid amobarbital injection (Wada and Rasmussen, 1960) with a standardized testing protocol (Intracarotid Amobarbital Test) and multiple regression and partial correlation analysis of subfield-specific hippocampal cell densities obtained from en bloc resected surgical specimens in the same patients. We identified 13 patients with an atypical CA1 predominant neuronal cell loss pattern, …