http://www.sciencedirect.com/science/article/pii/S1388245705001410
Hippocampal-orbitofrontal connectivity in human: An electrical
stimulation study H. Catenoixa, d, M. Magninb, d, M. Gu*notc, d,
J. Isnarda, d, F. Maugui*rea, d, P. Ryvlina, d, , Show more
Abstract Objective The identification of the pathways involved
in seizure propagation remains poorly understood in humans. For
instance, the respective role of the orbitofrontal cortex (OFC)
and of the commissural pathways in the interhemispheric
propagation of mesial temporal lobe seizures (mTLS) is a matter
of debate. In order to address this issue, we have directly
tested the functional connectivity between the hippocampus and
the OFC in 3 epileptic patients undergoing an intra-cranial
stereotactic EEG investigation. Methods Bipolar electrical
stimulations, consisting of two series of 25 pulses of 1 ms
duration, 0.2 Hz frequency, and 3 mA intensity, were delivered
in the hippocampus. Evoked potentials (EPs) were analysed for
each series, separately. Grand average of reproducible EPs was
then used to calculate latency of the first peak of each
individual potential. Results Hippocampal stimulations evoked
reproducible responses in the OFC in all 3 patients, with a mean
latency of the first peak of 222 ms (range: 185*258 ms).
Conclusions Our data confirm a functionnal connectivity between
the hippocampus and the OFC in human. Significance This
connectivity supports the potential role of the OFC in the
propagation of mTLS. Keywords Epilepsy; hippocampus;
Orbito-frontal cortex; Intra-cranial electrical stimulation;
Connectivity Corresponding author. Address: H*pital
Neurologique, 59 Bd Pinel, Lyon 69003, France. Tel.: +33 4 72 35
79 02; fax: +33 4 72 35 73 97.
Medial temporal lobe
The medial temporal lobe consists of structures that are vital
for declarative or long-term memory. [1]Declarative (denotative)
or [2]explicit memory is conscious memory divided into
[3]semantic memory (facts) and [4]episodic memory
(events).^[5][4]^:194 Medial temporal lobe structures that are
critical for long-term memory include the hippocampus, along
with the surrounding [6]hippocampal region consisting of the
[7]perirhinal, [8]parahippocampal, and [9]entorhinal neocortical
regions.^[10][4]^:196 The hippocampus is critical for memory
formation, and the surrounding medial temporal cortex is
currently theorized to be critical for memory
storage.^[11][4]^:21 The [12]prefrontal and visual cortices are
also involved in explicit memory.^[13][4]^:21 Research has shown
that lesions in the hippocampus of monkeys results in limited
impairment of function, whereas extensive lesions that include
the hippocampus and the medial temporal cortex result in severe
impairment.^[14][5] Functionally distinct pathways for auditory
processing in the orbitofrontal cortex include a rostral stream
associated with phonetic processing, and a more caudal stream
terminating just posterior to the orbitofrontal cortex in the
periarcuate prefrontal cortex associated with auditory-spatial
processing, though these connections share extensive overlap.
Both ventral and dorsal visual streams share connections with
orbitofrontal cortical areas, including rich projections to and
from the superior temporal pole, important for integration of
spatial and object processing.^[15][8]
http://en.wikipedia.org/wiki/Orbitofrontal_cortex
References
Visible links
1. Declarative memory
http://en.wikipedia.org/wiki/Declarative_memory
2. Explicit memory
http://en.wikipedia.org/wiki/Explicit_memory
3. Semantic memory
http://en.wikipedia.org/wiki/Semantic_memory
4. Episodic memory
http://en.wikipedia.org/wiki/Episodic_memory
5.
http://en.wikipedia.org/wiki/Temporal_lobe#cite_note-smith07-4
6. Hippocampal formation
http://en.wikipedia.org/wiki/Hippocampal_formation
7. Perirhinal cortex
http://en.wikipedia.org/wiki/Perirhinal_cortex
8. Parahippocampal gyrus
http://en.wikipedia.org/wiki/Parahippocampal_gyrus
9. Entorhinal cortex
http://en.wikipedia.org/wiki/Entorhinal_cortex
10.
http://en.wikipedia.org/wiki/Temporal_lobe#cite_note-smith07-4
11.
http://en.wikipedia.org/wiki/Temporal_lobe#cite_note-smith07-4
12. Prefrontal cortex
http://en.wikipedia.org/wiki/Prefrontal_cortex
13.
http://en.wikipedia.org/wiki/Temporal_lobe#cite_note-smith07-4
14.
http://en.wikipedia.org/wiki/Temporal_lobe#cite_note-5
15.
http://en.wikipedia.org/wiki/Orbitofrontal_cortex#cite_note-Cavada-8
