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Χωρίς Τίτλο!
Christos Paschalidis, MSc
PhD candidate,
Medical School of the University of Crete &
Institute of Molecular Biology and Biotechnology, FORTH
Thursday, June 18, 2026
14:00-15:00
=
<https://uoc-gr.zoom.us/j/89812825746?pwd=3DdMF6fnZazDjbsWVU3MMSr3jEnmPqs=
W.1> Alumni of the BRAIN and MIND Sciences Seminar Series ZOOM LINK
Meeting ID: 898 1282 5746
Passcode: 703942
Info: Vassilis Raos, 4512, <mailto:raos@xxxxxx> raos@xxxxxx
The speaker:
Christos Paschalidis
BSc in Mathematics, National and Kapodistrian University of Athens, =
2018; MSc in Brain and Mind Sciences, School of Medicine, University of =
Crete, 2023; PhD Candidate, School of Medicine, University of Crete, =
2023-present; Thesis: Understanding the organization and functioning of =
populations of neurons contributing to the visual description of objects =
using modern computational methods; Medical School University of Crete & =
Systems Neuroscience Lab Institute of Molecular Biology and =
Biotechnology (IMBB-FORTH); Supervisor: Dr Emmanouil Froudarakis.
My research interests focus on how neuronal population activity gives =
rise to our perception of the external world, particularly object =
perception. I investigate this question through the lens of geometry, =
studying how neural activity forms manifolds that link population-level =
responses with mathematical principles of representation and =
computation.
=20
Summary of the presentation:
Object recognition is fundamental to visual perception: we depend on it =
thousands of times each day. Even a single object can produce countless =
retinal images as either we or the object move in space. A striking =
achievement of the visual system is its ability to transform this =
continuous flow of external information into stable, recognizable =
perceptions of objects. A long-standing hypothesis suggests that the =
visual system solves this problem by progressively transforming visual =
input along the cortical hierarchy, generating increasingly complex =
population representations whose structure reflects the computations =
required for perception. However, characterizing such representations =
across thousands of neurons remains a challenge.
We use mesoscopic two-photon calcium imaging to record simultaneously =
from hundreds of neurons in the mouse visual cortex while head-fixed =
mice viewed four objects undergoing transformations, including changes =
in size, position, and rotation. Recordings were obtained from primary =
visual cortex and higher-order visual areas. We examine the geometrical =
properties of these population responses across mice, visual areas, =
asking how object-related neural manifolds are organized and transformed =
across the visual hierarchy. The characterization of these manifolds, =
their dimension, radius, and separability, reveal how visual areas =
transform sensory inputs into stable, behaviorally useful =
representations. To probe how these representations are shaped, we first =
examine behavioral state as a natural modulation of cortical processing. =
We then compare biological data with in-silico mouse models to test =
which aspects of object-manifold geometry current models capture.
Our results support a geometric view of object coding, where stronger =
higher-area information is reflected in manifold geometry.
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style=3D'font-size:11.0pt;mso-fareast-language:EN-US'>=CE=98=CE=95=CE=9C=CE=
=91</span><span lang=3DEN-US =
style=3D'font-size:11.0pt;mso-fareast-language:EN-US'>: Alumni of the =
BRAIN and MIND Sciences Seminar Series<o:p></o:p></span></p><p =
class=3DMsoNormal><span =
style=3D'font-size:11.0pt;mso-fareast-language:EN-US'>=CE=91=CE=A0=CE=9F=CE=
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style=3D'font-size:11.0pt;mso-fareast-language:EN-US'>: </span><span =
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Vasileios </span><span =
style=3D'font-size:11.0pt;font-family:"Calibri",sans-serif'><a =
href=3D"mailto:vraos@xxxxxxxxxx";><span =
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class=3DMsoNormal><span lang=3DEN-US =
style=3D'font-size:11.0pt;mso-fareast-language:EN-US'><a =
href=3D"https://news.uoc.gr/news/2026/12-06/B&M_ALUMNI_seminars_ANNOU=
NCEMENT_Paschalidis.pdf">https<span lang=3DEL>://</span>news<span =
lang=3DEL>.</span>uoc<span lang=3DEL>.</span>gr<span =
lang=3DEL>/</span>news<span lang=3DEL>/2026/12-06/</span>B<span =
lang=3DEL>&</span>M<span lang=3DEL>_</span>ALUMNI<span =
lang=3DEL>_</span>seminars<span lang=3DEL>_</span>ANNOUNCEMENT<span =
lang=3DEL>_</span>Paschalidis<span lang=3DEL>.</span>pdf</a></span><span =
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</span><span =
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class=3DMsoNormalTable border=3D0 cellpadding=3D0 width=3D"100%" =
style=3D'width:100.0%;background:white'><tr><td width=3D"100%" =
style=3D'width:100.0%;padding:.75pt .75pt .75pt .75pt'><p =
class=3DMsoNormal align=3Dcenter =
style=3D'text-align:center'><strong><span lang=3DEN-US =
style=3D'font-size:18.0pt;font-family:"Arial",sans-serif;color:#0837F7'>A=
lumni of the BRAIN and MIND Sciences Seminar Series</span></strong><span =
lang=3DEN-US><o:p></o:p></span></p></td></tr></table><p align=3Dcenter =
style=3D'text-align:center;background:white'><strong><span =
style=3D'font-size:14.0pt;font-family:"Arial",sans-serif;color:#0837F7'>F=
rom Object Recognition to Neural Manifolds: Population Geometry in Mouse =
Visual Cortex</span></strong><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif'><o:p></o:p></=
span></p><p align=3Dcenter =
style=3D'text-align:center;background:white'><strong><span =
style=3D'font-size:14.0pt;font-family:"Arial",sans-serif;color:#0837F7'>C=
hristos Paschalidis, MSc</span></strong><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif;color:black'><=
br></span><strong><span =
style=3D'font-size:14.0pt;font-family:"Arial",sans-serif;color:#0837F7'>P=
hD candidate,</span></strong><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif;color:black'><=
br></span><strong><span =
style=3D'font-size:14.0pt;font-family:"Arial",sans-serif;color:#0837F7'>M=
edical School of the University of Crete &</span></strong><b><span =
style=3D'font-size:14.0pt;font-family:"Arial",sans-serif;color:#0837F7'><=
br><strong><span style=3D'font-family:"Arial",sans-serif'>Institute of =
Molecular Biology and Biotechnology, =
FORTH</span></strong></span></b><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif'><o:p></o:p></=
span></p><table class=3DMsoNormalTable border=3D0 cellpadding=3D0 =
width=3D"100%" style=3D'width:100.3%;background:white'><tr><td =
width=3D"36%" style=3D'width:36.34%;padding:.75pt .75pt .75pt .75pt'><p =
align=3Dcenter style=3D'text-align:center'><strong><span =
style=3D'font-size:14.0pt;font-family:"Arial",sans-serif;color:#0837F7'>T=
hursday, June 18, 2026</span></strong><o:p></o:p></p></td></tr><tr><td =
width=3D"36%" style=3D'width:36.34%;padding:.75pt .75pt .75pt .75pt'><p =
align=3Dcenter style=3D'text-align:center'><strong><span =
style=3D'font-size:14.0pt;font-family:"Arial",sans-serif;color:#0837F7'>1=
4:00-15:00</span></strong><o:p></o:p></p></td></tr><tr><td width=3D"36%" =
style=3D'width:36.34%;padding:.75pt .75pt .75pt .75pt'><p align=3Dcenter =
style=3D'text-align:center'><strong><span =
style=3D'font-family:"Arial",sans-serif;color:#0837F7'><a =
href=3D"https://uoc-gr.zoom.us/j/89812825746?pwd=3DdMF6fnZazDjbsWVU3MMSr3=
jEnmPqsW.1" target=3D"_blank"><span =
style=3D'font-size:14.0pt;color:#0837F7'>Alumni of the BRAIN and MIND =
Sciences Seminar Series ZOOM =
LINK</span></a></span></strong><o:p></o:p></p><p align=3Dcenter =
style=3D'text-align:center'><span =
style=3D'font-family:"Arial",sans-serif;color:#0837F7'>Meeting ID: 898 =
1282 5746</span><o:p></o:p></p><p align=3Dcenter =
style=3D'text-align:center'><span =
style=3D'font-family:"Arial",sans-serif;color:#0837F7'>Passcode: =
703942</span><o:p></o:p></p></td></tr></table><p =
style=3D'background:white'><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif;color:black'>I=
nfo: Vassilis Raos, 4512, </span><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif;color:#0837F7'=
><a href=3D"mailto:raos@xxxxxx";><span =
style=3D'color:#0837F7'>raos@xxxxxx</span></a></span><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif'><o:p></o:p></=
span></p><p style=3D'background:white'><strong><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif;color:black'>T=
he speaker:</span></strong><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif'><o:p></o:p></=
span></p><p><em><b><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif'>Christos =
Paschalidis</span></b></em><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif'><o:p></o:p></=
span></p><p><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif'>BSc in =
Mathematics, National and Kapodistrian University of Athens, 2018; MSc =
in Brain and Mind Sciences, School of Medicine, University of Crete, =
2023; PhD Candidate, School of Medicine, University of Crete, =
2023-present; Thesis: Understanding the organization and functioning of =
populations of neurons contributing to the visual description of objects =
using modern computational methods; Medical School University of Crete =
& Systems Neuroscience Lab Institute of Molecular Biology and =
Biotechnology (IMBB-FORTH); Supervisor: Dr Emmanouil =
Froudarakis.<o:p></o:p></span></p><p><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif'>My research =
interests focus on how neuronal population activity gives rise to our =
perception of the external world, particularly object perception. I =
investigate this question through the lens of geometry, studying how =
neural activity forms manifolds that link population-level responses =
with mathematical principles of representation and =
computation.<o:p></o:p></span></p><p><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif'> <o:p></=
o:p></span></p><p><strong><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif'>Summary of =
the presentation:</span></strong><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif'><o:p></o:p></=
span></p><p><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif'>Object =
recognition is fundamental to visual perception: we depend on it =
thousands of times each day. Even a single object can produce countless =
retinal images as either we or the object move in space. A striking =
achievement of the visual system is its ability to transform this =
continuous flow of external information into stable, recognizable =
perceptions of objects. A long-standing hypothesis suggests that the =
visual system solves this problem by progressively transforming visual =
input along the cortical hierarchy, generating increasingly complex =
population representations whose structure reflects the computations =
required for perception. However, characterizing such representations =
across thousands of neurons remains a =
challenge.<o:p></o:p></span></p><p><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif'>We use =
mesoscopic two-photon calcium imaging to record simultaneously from =
hundreds of neurons in the mouse visual cortex while head-fixed mice =
viewed four objects undergoing transformations, including changes in =
size, position, and rotation. Recordings were obtained from primary =
visual cortex and higher-order visual areas. We examine the geometrical =
properties of these population responses across mice, visual areas, =
asking how object-related neural manifolds are organized and transformed =
across the visual hierarchy. The characterization of these manifolds, =
their dimension, radius, and separability, reveal how visual areas =
transform sensory inputs into stable, behaviorally useful =
representations. To probe how these representations are shaped, we first =
examine behavioral state as a natural modulation of cortical processing. =
We then compare biological data with in-silico mouse models to test =
which aspects of object-manifold geometry current models =
capture.<o:p></o:p></span></p><p><span =
style=3D'font-size:10.0pt;font-family:"Verdana",sans-serif'>Our results =
support a geometric view of object coding, where stronger higher-area =
information is reflected in manifold =
geometry.<o:p></o:p></span></p></div></body></html>
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