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\begin{document}

\title{Obtaining novel data-driven hypotheses from teaching activities: an
example assessing the role of the FKBP5 gene in major depression}



\author[1]{Heather Strelevitz}%
\author[1]{Alireza Dehaqani}%
\author[1]{Luigi Balasco}%
\author[1]{Yuri Bozzi}%
\affil[1]{Universita degli Studi di Trento}%


\vspace{-1em}



  
  \date{June 18, 2024}


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\selectlanguage{english}
\begin{abstract}
Many clinical and research efforts aim to develop antidepressant drugs
for those suffering from major depressive disorder (MDD). Yet even
today, the available treatments are suboptimal and unpredictable, with a
significant proportion of patients enduring multiple drug attempts and
adverse side effects before a successful response; and for many
patients, no response at all. Thus, a clearer understanding of the
mechanisms underlying MDD is necessary. In the ``Brain Development and
Disease'' class of our Master's program in Cognitive Sciences, we ask
students to collect data about the expression of a gene whose altered
expression and/or function is related to a brain disorder. The students'
final exam assignment consists of writing a research article in which
the collected data are discussed in relation to the relevant disorder.
In the course of one of these assignments, we identified the FKBP5 gene
as a key player uniting two major hypotheses of MDD pathogenesis and
treatment response. FKBP5 controls biological processes including
immunoregulation and glucocorticoid function, both of which are
separately implicated in the development and prognosis of MDD. Gene
expression analyses from the human, non-human primate, and mouse Allen
Brain Atlases revealed that FKBP5 is expressed in brain regions involved
in MDD, particularly at ages susceptible to early-life stressors. Data
re-analysis from published studies confirmed that FKBP5 expression is
upregulated in relevant brain regions in human MDD and preclinical mouse
models of MDD. Our experience shows that classes engaging students in
data collection and analysis projects may effectively result in novel
data-driven hypotheses.%
\end{abstract}%



\sloppy


\textbf{INTRODUCTION}

The ``Brain Development and Disease'' class of the Master's Degree in
Cognitive Science at the University of Trento focuses on brain
development's molecular and cellular mechanisms. Gene networks
controlling embryonic brain development, neural plasticity during
critical periods, and the pathogenesis of neurodevelopmental disorders
are the key subjects addressed in this class. The class aims to give the
students a comprehensive overview of brain development, addressing the
neurobiological underpinnings of neural development and the possible
pathological consequences of their derangement. For their final exam,
students are asked to write a research article in which they must
describe the expression profile of one gene of their interest, whose
altered expression and function has been related to a brain disorder. We
acknowledge that studying the expression of one gene at a time has its
limitations, since brain disorders are likely of multifactorial origin
and their pathogenic mechanisms involve differential dysregulation of
several genes. However, for didactic reasons, we think that the study of
the expression of one single gene related to a brain disorder is largely
enough for students to generate an adequate amount of data for their
exam. To achieve this goal, students have to collect gene expression
data from the mouse, primate and human Allen Brain Atlases and discuss
the data with respect to the disorder of interest. The teacher first
provides the students with a tutorial helping them to familiarize with
gene expression data collection and analysis. Then, students can
practice data collection during class hours and online, plus one-to-one
sessions with a tutor flanking the teacher. We previously published a
brief report of one of these class activities (Rubino \& Bozzi, 2021).
Here we describe, in a more extensive way, a new study resulting from
our students' work.

Early life stress (ELS) plays a causal role in many psychiatric
disorders, including major depressive disorder (MDD; Cheng et al.,
2022). ELS is relevant to one of the most robust hypotheses of MDD
mechanism: impairment of the hypothalamus-pituitary-adrenal (HPA) axis.
Patients have increased levels of both cortisol and
corticotropin-releasing hormone (CRH) as a result of disruption of the
glucocorticoid receptor (GR) signaling (Ising et al., 2007). GR
signaling disruption then results in impaired feedback inhibition along
the HPA axis (de Kloet et al., 2005). In particular, ELS induces
lifelong disturbances to HPA function, thereby increasing vulnerability
to MDD later in life (Cheng et al., 2022). Importantly, improved HPA
system regulation (as measured by stress hormone response to a
dexamethasone/CRH test) is associated with enhanced response to
treatment (Ising et al., 2007). However, these findings have not yielded
clinically successful medications (Malhi and Mann, 2018).

Neuroinflammation is another critical player in MDD pathogenesis. Not
only does immune system activation induce symptoms that overlap with
those of MDD, but patients with neuroinflammatory diseases also have a
high prevalence of MDD (Setiawan et al., 2015). Elevated proinflammatory
cytokines are reliably found in patients with MDD; and, remarkably,
therapeutically administered cytokines trigger depression approximately
half the time (Raison et al., 2006). Although this systemic immune
activation has been highly studied as a component of MDD, very little is
agreed upon regarding the role or mechanism of action for cytokines in
the brain (Beurel et al., 2020).

Despite monumental research efforts spanning decades, MDD
pathophysiology is not clear (Malhi and Mann, 2018). Consequently,
comprehension of its pharmacological treatment is also insufficient. Low
antidepressant acceptability is mainly due to weeks of delay before the
full effect, and the adverse side effects that can occur during and
after that waiting period (David and Gourion, 2016). Moreover, up to
15\% of MDD patients struggle with little to no response to
pharmacological interventions (Berlim and Turecki, 2007), with clinical
guidance limited to trial and error. The scientific community is at a
loss to explain why some patients must suffer through failed treatment
attempts while others do not (Grogans et al., 2022). There are no
clinically relevant methods for predicting which antidepressant may work
best for a given individual (Zeier et al., 2018).

The human FKBP5 gene codes for FK506-binding protein 5, a prolyl
isomerase that binds immunosuppressive drugs such as FK506, rapamycin,
and cyclosporin A. FKBP5 is located on chromosome 6 and its protein
product functions as a cochaperone of heat-shock 90-kD protein-1 (OMIM,
Online Mendelian Inheritance in Man, http://omim.org/, OMIM \#602623;
Gene ID 2289, https://www.ncbi.nlm.nih.gov/gene/2289). FKBP5 codes for
an immunophilin, which performs immunoregulation and basic cellular
functions. FKBP5 is also related to glucocorticoid signaling (Vermeer et
al., 2003) and consequently the stress regulation system. Moreover,
FKBP5 alternations in mice have been shown to affect stress responses
through HPA axis activity, inflammation, and depressive- and
anxiety-like behaviors (H\selectlanguage{ngerman}äusl et al., 2021; Gan et al., 2022). This gene
may help explain how the HPA axis and immune system mediate
antidepressant efficacy. In the course of a student's assignment, we
identified the FKBP5 gene as a key player uniting these two major
hypotheses of MDD pathogenesis and treatment response.

\textbf{MATERIALS AND METHODS}

\emph{Data collection.} This research effort proceeded by mining
existing data and literature available online. mRNA expression
information was drawn from microarray and transcriptome datasets
available on the Allen Brain Atlases portal
(https://portal.brain-map.org). Data were not available for mouse brain
development (http://developingmouse.brain-map.org\emph{)} , so we
analyzed the prenatal and postnatal expression FKBP5 mRNA only in the
rhesus macaque (\emph{Macaca mulatta} ) and human (\emph{Homo sapiens} )
brain. Regions of interest (ROIs) including prefrontal cortex, amygdala,
hippocampus, and striatum were selected on the basis of their
involvement in MDD and ELS (Criado-Marrero et al, 2020; Troubat et al.,
2021; Grogans et al., 2022; Pizzagalli and Roberts, 2022). The primary
visual cortex was included as an independent region in the figure as an
example of a non-ROI, to highlight the differences between gene
expression for an individual region which is not relevant to MDD, and
those which are. Adult mouse FKBP5 mRNA expression data were also
retrieved from the Allen Brain Atlases portal
(http://mouse.brain-map.org/gene/show/14006; experiment 70525820, probe
name RP\_050317\_04\_G06). For the re-analyses of FKBP5 mRNA expression
in human and mouse MDD, data were retrieved from the original
publications. Human MDD RNA sequencing (RNAseq) data (Matosin et al.,
2023) consisted of PFC (area BA9) samples from 179 control subjects and
144 MDD cases, previously described in Tao et al. (2017). RNAseq data
from a mouse model of MDD were retrieved from
https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE109315. In this
study, the authors performed RNAseq on prefrontal cortex and hippocampus
from adult C57BL/6N control mice and C57BL/6N mice subjected to chronic
social defeat stress (CSDS); data were normalized using voom and
adjusted for sequencing (vHPC) and library preparation batches (vHPC,
mPFC) with ComBat (Laine et al., 2018).

\emph{Data analysis.} The human developmental transcriptome and
non-human primate (NHP) microarray microdissection data for the FKBP5
gene were analyzed with Matlab (Mathworks) using the toolbox cbrewer2
version 1.0.0.1 (Lowe, 2023) to generate heat maps. The log2 reads per
kilobase per million (RPKM) values of transcriptome data and z-score
normalized values of microarray data (probe MmugDNA.10638.1.S1\_at) were
averaged for donors of the same age, and also across substructures to
achieve the macrostructures (for example, the V1 macrostructure is
composed of substructures including layer I, layer II, etc.).
Supplementary Table 1 reports a full list of the components included in
each macrostructure. In the case of the human data, any time point which
lacked results for more than three macrostructures was excluded.
Supplementary Table 2 summarizes the number of subjects per time point
for the human data, while Supplementary Table 3 reports the same
information for the corresponding non-human primate data points. FKBP5
mRNA expression data from the MDD mouse model (Laine et al. 2018; GEO
accession number GSE109315) were analyzed with Matlab (Mathworks). FKBP5
mRNA expression data from RNAseq human datasets were re-plotted from
Figure 1a of the original paper (Matosin et al., 2023) and analyzed
using Prism 8.0 (GraphPad).

\emph{Code Accessibility.} The code described in this paper is freely
available online on Zenodo
(\emph{https://doi.org/10.5281/zenodo.7525970} ) and GitHub
(\emph{https://github.com/BozziNDRLab/Strelevitz\_et\_al\_2023.git} ).
The specific toolbox we used in the code was obtained from Lowe (2023).

\textbf{RESULTS}

FKBP5 mRNA expression in the non-human primate (NHP) and human brains
was analyzed over a range of prenatal and postnatal ages. Figure 1A
summarizes the data analysis workflow. Microarray data from NHP brain
development showed an interesting pattern at postnatal ages. FKBP5 mRNA
was detected in regions of interest (ROIs) relevant to MDD (prefrontal
cortex, hippocampus, amygdala, and striatum) at 0, 3, and 12 months.
During this range of time, FKBP5 had a much stronger expression in the
ROIs than in other brain regions. By 48 months, FKBP5 expression was
detected in all brain regions. Moreover, within the ROIs, there was a
sharp contrast between time points before birth and after birth: FKBP5
expression was only apparent after birth (Fig. 1B).

Similarly, the study of FKBP5 mRNA transcriptome expression in the human
prefrontal cortex, hippocampal formation, amygdaloid complex, and
striatum at early postnatal ages confirmed what was already observed in
NHPs (Fig. 1B). In particular, FKBP5 expression at 2, 3, 8, 11, and 13
years was strongly upregulated for ROIs in comparison to other brain
regions. Again, it is clear that FKBP5 mRNA expression increases
strongly after birth. The evidence that the gene turns on soon after
birth would suggest that FKBP5 is vulnerable to being altered by the
animal's interaction with the environment, and thereby ELS. Further,
this effect is observed specifically in regions involved with MDD. FKBP5
mRNA expression were not available from the developing mouse brain Allen
atlas (http://developingmouse.brain-map.org). However, \emph{in
situ}hybridization data from the adult C57BL/6 mouse Allen atlas
confirmed that FKBP5 mRNA is highly expressed in MDD-relevant regions
such as the prefrontal cortex and hippocampus (Fig. 2).

These observations led us to verify whether FKBP5 mRNA expression was
deregulated in the brain of a mouse model of MDD as well as human MDD.
To this end, we analyzed RNAseq data from the medial prefrontal cortex
(mPFC) and ventral hippocampus (vHPC) of C57BL/6 control mice and
C57BL/6 mice subjected to chronic social defeat stress (CSDS) (Laine et
al., 2018), a widely used model of MDD. In the mPFC, we detected an
up-regulation of FKBP5 mRNA in CSDS mice compared to age-matched
controls (Fig. 3A, left; CSDS vs. control, t-test p\textless{}0.01;
rank-sum test, p\textless{}0.01). A trend to an up-regulation of FKBP5
mRNA was also detected in the vHPC of CSDS mice (Fig. 3A, right; CSDS
vs. control, t-test p\textless{}0.05; rank-sum test, p=0.08333). A
significant up-regulation of FKBP5 mRNA in the prefrontal cortex was
also detected in human MDD patients compared to control subjects (Fig.
3B; MDD vs. control, p\textless{}0.001, Mann Whitney test; data
re-analyzed Cohort 1 / Figure 1a of Matosin et. al., 2023). Thus, the
up-regulation of FKBP5 mRNA observed in the PFC of human MDD patients
and socially-defeated mice confirms our idea of a prominent role of
FKBP5 in MDD.



\textbf{DISCUSSION}

In this study, we show that FKBP5 mRNA expression turns on at birth in
brain areas involved in MDD, such as the hippocampal formation,
amygdala, and striatum. According to previous work describing the link
between FKBP5, HPA axis and MDD, these data allow us to postulate that
FKBP5 expression is vulnerable to ELS, and we propose a key role of
FBKP5 in MDD pathogenesis.

\emph{The role of FKBP5 for ELS and HPA axis.} FKBP5 regulates GR
sensitivity, a fact which is intertwined with the HPA hypothesis of MDD.
For patients with MDD, FKBP5 polymorphisms have been associated with the
extent of GR signaling dysregulation (Menke et al., 2013). DNA
methylation alterations in stress-regulating genes such as FKBP5, are,
in fact, the cause of long-lasting effects of ELS (Wiechmann et al.,
2019). Taking ELS into account illuminates the circular relationship
between FKBP5 and the physiological stress response. Exposure to ELS --
which is essentially a challenge to the glucocorticoid system - creates
lifelong changes within the FKBP5 gene regulatory regions (Wiechmann et
al., 2019). These stress-induced changes to FKBP5 DNA methylation
further impact an individual's stress regulation system, disposing them
to developing a disorder such as MDD (Wiechmann et al., 2019). This
mechanism has been demonstrated in detail in rodents, implicating the
hippocampus for long-term FKBP5 alterations brought on by ELS, which
increase vulnerability to depressive-like behaviors (Xu et al., 2019).

\emph{The role of FKBP5 for immunoregulation.} Despite our focus on a
psychiatric disorder, we must not ignore the rest of the body simply
because it is not the brain, especially considering the role of FKBP5 in
immune function. For humans, FKBP5 is broadly expressed throughout
multiple bodily systems (unsurprisingly due to its essential cellular
functions), but it is most strongly expressed in immune system tissues.
According to GeneCards (Safran et al., 2022), FKBP5 is overexpressed in
lymph nodes and peripheral blood mononuclear cells. As mentioned, FKBP5
functions as a co-chaperone for a heat shock protein. These are
molecules that, as a part of the innate immune system, can signal cell
damage to recruit other immune cells to the site of insult (Gong et al.,
2020). Such activation promotes inflammation to aid with regenerative
processes, but excess may result in further disease (Gong et al., 2020),
including psychiatric disorders like MDD. It is also worth mentioning
that ELS causes persistent alterations in peripheral inflammation
(Baumeister et al., 2016), thus tying together the stress and immune
sides of the story.

\emph{Putting it all together: the role of FKBP5 for antidepressant
treatment.} The HPA axis and immune systems individually affect
antidepressant efficacy. For instance, there are numerous reports that
ELS (which impairs the HPA stress regulation) substantially reduces
antidepressant response (Nanni et al., 2012; Williams et al., 2016;
Menke et al., 2021). Moreover, inflammatory markers decrease after MDD
treatment, and non-responders have higher inflammation at baseline
(Strawbridge et al., 2015). Some studies also indicate inflammation is
associated with poor antidepressant response (Vogelzangs et al., 2014).
These are exciting findings, and could have broad implications for
predicting individual treatment success or even creating new
pharmaceutical options. Yet the crucial insight here is the connection
provided by the gene FKBP5, with a particular influence from ELS, which
offers a more comprehensive explanation of a complex and often variable
conundrum. FKBP5 has been associated with unipolar depression (Zobel et
al., 2010) and even treatment response for depression (Lekman et al.,
2008). Severe life events significantly alter FKBP5 mRNA expression,
which tends to normalize after four weeks of antidepressants (Menke et
al., 2021). ELS-induced alterations of FKBP5 expression even change the
expression of other glucocorticoid-related genes (Yeo et al., 2017). For
its GR-modulating properties and consequent connection to the HPA axis,
FKBP5 polymorphisms have been studied and found to be associated with
faster response to antidepressants (Binder et al., 2004). Lastly and
most strikingly, FKBP5 deletion in the mouse results in antidepressant
behavior, with no change to other motor or cognitive functions (O'Leary
et al., 2011). Such a direct intervention to FKBP5 itself, and with such
precise effects, strongly supports our idea that this gene is a vital
functional link between two large-scale processes which mediate the
success or failure of antidepressants. This evidence aligns with our
findings of FKBP5 expression, anatomically and throughout human and NHP
brain development (Fig. 1), as well as with the finding (Fig. 3) that
FKBP5 expression is upregulated in MDD both clinical (Matosin et al.,
2023) and preclinical settings (Laine et al., 2018).

\emph{Limitations and future directions.} This research effort is
limited by its observational nature. Nevertheless, it is important to
point out that our results, initially obtained from supposedly control
subjects (Fig. 1B) and extrapolated to their potential relevance for
MDD, were then validated in clinical and preclinical datasets (Fig. 3).
Further, the low number of subjects analyzed at each time point in the
developmental study (Fig. 1B) might have reduced the power of our data.
This is an intrinsic limitation of the Allen Brain Atlases, which are
built on a relatively low number of experimental subjects. However, the
finding that FKBP5 mRNA expression is upregulated in both human MDD
(Matosin et al., 2023) and mouse models of the disorder (Laine et al.,
2018) (see also Fig. 3) strengthens our hypotheses that FKBP5
dysfunction is linked to two major causes of MDD and to the response to
antidepressant treatment. In order to verify whether FKBP5 expression is
normalized by antidepressant treatment, future work might be extended to
human and mouse gene expression datasets containing control subjects and
subjects treated with antidepressant drugs.

We also acknowledge that studying the expression of one single gene
related to MDD does not allow us to unravel the transcriptional
complexity of this disorder, which clearly has a multifactorial origin.
However, our long (\textgreater{} 5 years) experience with this type of
interactive teaching activity showed us that this simplified view (``one
gene -- one disease'') allows students to generate an adequate amount of
data for their final exam and, most importantly, to mechanistically
address the function of a specific gene in the pathogenesis of a complex
brain disease.

\emph{Considerations on practical coursework.} In this study, we
described an example of how a teaching approach engaging students in
practical coursework may contribute to generate scientifically
meaningful results and novel data-driven hypotheses. Most importantly,
we think this approach positively contributes to the students'
educational experience. First, students learn to collect and analyze
data from publicly accessible sources, becoming familiar with open
science methods; this provides students with new skills that might
become useful for real research projects in the laboratory. In addition,
being asked to write a research article for their final exam, students
develop or improve scientific writing skills in preparation of their
Master's thesis. Lastly, our Master Degree in Cognitive Sciences does
not include bioinformatic classes, though students do acquire advanced
skills in programming and data analysis. Thus, our approach gives
students the opportunity to become familiar with bioinformatic
techniques.

We acknowledge that a randomization strategy with course delivery would
help to quantitatively address the advantages of this educational
experience. However, such a strategy is far beyond the scope of this
approach: our aim is to develop an interactive teaching approach that
helps students develop new skills. We thus think it might be interesting
to share our experience with the neuroscience community. Our experience
shows that classes aiming at involving students in projects requiring
data collection and analysis from publicly available gene expression
databases (such as the Allen Brain Atlases) may effectively result in
new ideas for neuroscience research.

\textbf{Acknowledgements.} The authors thank the staff of the Master in
Cognitive Sciences (CIMeC, University of Trento) for excellent
administrative assistance, Prof. Enrico Domenici (CIBIO, University of
Trento) for insightful comments, and Prof. Elizabeth Binder (Department
of Translational Research in Psychiatry, Max-Planck Institute of
Psychiatry, Munich, Germany) for allowing data re-analysis from Matosin
et al., 2023 (Fig. 1a).

\textbf{Competing Interests.} The authors declare no competing financial
interests.

\textbf{Author Contributions:} HS wrote the paper and contributed to
making the figures; AD analyzed the data and contributed to making the
figures; LB supervised students' activities, analyzed the data, and
contributed to making the figures; YB designed the project, analyzed
data, contributed to making the figures, and edited the manuscript. This
research was not supported by any specific grant from any funding
agency.

\textbf{Data accessibility.} This study made use of freely available
data from Allen Brain Atlas and Gene Expression Omnibus. The code used
to analyze data is freely available online on Zenodo and GitHub (see
details in the Materials and Methods section).

\textbf{Abbreviations.} AMG, amygdaloid complex; CB, cerebellum; Ctrl,
control; CRH, corticotropin-releasing hormone; CSDS, chronic social
defeat stress; CTXsp, cortical subplate; dHPC, dorsal hippocampus; ELS,
early life stress; GEO, Gene Expression Omnibus database; GR,
glucocorticoid receptor; HPA, hypothalamus-pituitary-adrenal axis; HPC,
hippocampus; HPF hippocampal formation; HY, hypothalamus; MB, midbrain;
MDD, major depressive disorder; mPFC, medial prefrontal cortex; MY,
medulla oblongata; NHP, non-human primate; OLF, olfactory areas; OMIM,
Online Mendelian Inheritance in Man database; P, pons; PAL, globus
pallidus; PFC, prefrontal cortex; RNAseq, RNA sequencing; ROI, region of
interest; STR, striatum; TH, thalamus; vHPC, ventral hippocampus; V1,
primary visual cortex.

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\textbf{Figure Legends}

\textbf{Figure 1.} Overview of the workflow for data collection and
analysis. Images are from the Allen Brain Atlas and Matlab (Mathworks).

\textbf{Figure 2} . FKBP5 mRNA is expressed in MDD-relevant brain
regions across species. A) Heat maps of FKBP5 mRNA expression in
selected regions of human and non-human primate (NHP) brains. Top)
Relative FKBP5 mRNA expression for selected human brain regions over
time; prenatal is expressed as post-conceptual weeks (pcw) and postnatal
is expressed as years (yrs). The category 30+ contains 30, 36, 37, and
40 years. Bottom) Relative FKBP5 mRNA expression for selected NHP brain
regions over time; prenatal is expressed as embryonic days (E) and
postnatal is expressed as months (mo). In both heat maps, a gray cell
indicates no data available. Regions analyzed were prefrontal cortex
(PFC), hippocampus (HPC), amygdaloid complex (AMG), striatum (STR),
primary visual cortex (V1), and all other available regions which are
not transitory (a transitory region only exists during finite embryonic
periods). The black lines connecting the two heat maps indicate the ages
which are developmentally similar between species (Kang et al., 2011;
Zhu et al., 2018). B) FKBP5 mRNA is expressed in the adult mouse brain
in areas relevant for MDD. Top) Log2 expression values of FKBP5 mRNA in
different brain regions, obtained from quantification of \emph{in
situ}hybridization data from the Allen mouse brain atlas. Abbreviations:
OLF, olfactory areas; HPF, hippocampal formation; CTXsp, cortical
subplate; STR, striatum; PAL, globus pallidus; TH, thalamus; HY,
hypothalamus; MB, midbrain; P, pons; MY, medulla oblongata; CB,
cerebellum. Bottom) Representative picture showing FKBP5 mRNA expression
on a sagittal section of the adult mouse brain. High and low expression
levels are in red/yellow and green/blue, respectively. Abbreviations:
PFC, prefrontal cortex; dHPC, dorsal hippocampus; vHPC, ventral
hippocampus; CB, cerebellum. Scale bar: 1.68 mm.

\textbf{Figure 3.} FKBP5 mRNA expression is upregulated in the
prefrontal cortex of socially defeated mice and MDD patients. A) FKBP5
mRNA expression (measured in CPM, counts per million) in the CSDS mouse
of MDD (defeated vs. controls; *p\textless{}0.05, t-test;
**p\textless{}0.01, t-test and rank-sum test; ``defeated'' indicates
mice subjected to CSDS). B) FKBP5 mRNA expression (measured as log2 of
fragments per kilobase million, FPKM log2) in human MDD (MDD vs.
controls, ****p\textless{}0.0001, Mann-Whitney test). Abbreviations:
Ctrl, control; PFC, prefrontal cortex; dHPC, dorsal hippocampus; vHPC,
ventral hippocampus.\selectlanguage{english}
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