Fornix problem: Why do lesions of the fornix, which connects the hippocampus (HF) to the medial mammillary nucleus (MMN), often cause no deficits in tasks severely affected by lesions of HF or MMN? Solution: The direct HF feedback to antero ventral (AV) thalamus (MMN [Rightarrow A: implies] AV [Leftrightarrow A: l&r dbl arrow] HF), which is blocked by MMN lesions but not fornix lesions, is sufficient for nonscene-relevant consolidation.

By utilizing new information from both clinical and experimental (lesion, electrophysiological, and gene-activation) studies with animals, the anatomy underlying anterograde amnesia has been reformulated. The distinction between temporal lobe and diencephalic amnesia is of limited value in that a common feature of anterograde amnesia is damage to part of an comprising the hippocampus, the fornix, the mamillary bodies, and the anterior thalamic nuclei. This view, which can be traced back to Delay and Brion (1969), differs from other recent models (...) in placing critical importance on the efferents from the hippocampus via the fornix to the diencephalon. These are necessary for the encoding and, hence, the effective subsequent recall of episodic memory. An additional feature of this hippocampalanterior thalamic and the perirhinal–medial dorsal thalamic systems are compromised, leading to severe deficits in both recall and recognition. (shrink)

Three experiments on neural grafting with adult rat hosts are described. Working memory impairments were produced by lesioning the hippocampus or severing its connections with the septum by ablating the fimbria-fornix. The results suggest that the survival and growth of a neural graft, whether an autograft or a xenograft, is not a necessary condition for functional recovery on a task tapping working memory.

Background: In prior reports, we described the design and initial performance of a fully implantable, bi-directional neural interface system for use in deep brain and other neurostimulation applications. Here we provide an update on the chronic, long-term neural sensing performance of the system using traditional 4-contact leads and extend those results to include directional 8-contact leads.Methods: Seven ovine subjects were implanted with deep brain stimulation leads at different nodes within the Circuit of Papez: four with unilateral leads in the anterior (...) nucleus of the thalamus and hippocampus; two with bilateral fornix leads, and one with bilateral hippocampal leads. The leads were connected to either an Activa PC+S® or Percept PC°ledR deep brain stimulation and recording device. Spontaneous local field potentials, evoked potentials, LFP response to stimulation, and electrode impedances were monitored chronically for periods of up to five years in these subjects.Results: The morphology, amplitude, and latencies of chronic hippocampal EPs evoked by thalamic stimulation remained stable over the duration of the study. Similarly, LFPs showed consistent spectral peaks with expected variation in absolute magnitude dependent upon behavioral state and other factors, but no systematic degradation of signal quality over time. Electrode impedances remained within expected ranges with little variation following an initial stabilization period. Coupled neural activity between the two nodes within the Papez circuit could be observed in synchronized recordings up to 5 years post-implant. The magnitude of passive LFP power recorded from directional electrode segments was indicative of the contacts that produced the greatest stimulation-induced changes in LFP power within the Papez network.Conclusion: The implanted device performed as designed, providing the ability to chronically stimulate and record neural activity within this network for up to 5 years of follow-up. (shrink)

The Thesaurus lists a number of texts where demolior appears as a passive. To these should be added Cicero, Topica 4.22: ‘Ab efficientibus rebus hoc modo. Omnibus est ius parietem directum ad parietem communem adiungere vel solidum vel fornicatum. Sed qui in pariete communi demoliendo damni infecti promiserit, non debebit prae-stare quod fornix viti fecerit. Non enim eius vitio qui demolitus est damnum factum est, sed eius operis vitio quod ita aedificatum est ut suspendi non posset.’.

The Thesaurus lists a number of texts where demolior appears as a passive. To these should be added Cicero, Topica 4.22: ‘Ab efficientibus rebus hoc modo. Omnibus est ius parietem directum ad parietem communem adiungere vel solidum vel fornicatum. Sed qui in pariete communi demoliendo damni infecti promiserit, non debebit prae-stare quod fornix viti fecerit. Non enim eius vitio qui demolitus est damnum factum est, sed eius operis vitio quod ita aedificatum est ut suspendi non posset.’.