Visual perception deficits in albinotic mammals - ferrets (Mustella putoriius furo) and rats (Rattus norvegiicus; strains Wistar and Long-Evans) [Elektronische Ressource] = Visuelle Wahrnehmungsdefizite albinotischer Säuger - Frettchen (Mustela putorius furo) und Ratten (Rattus norvegicus; Stämme Wistar und Long-Evans) / vorgelegt von Daniela Hupfeld

De
VViissuuaall ppeerrcceeppttiioonn ddeeffiicciittss iinn aallbbiinnoottiicc mmaammmmaallss ––ferrets (Mustela putorius furo) and rats (Rattus norvegicus; strains Wistar and Long-Evans) Visuelle Wahrnehmungsdefizite albinotischer Säuger – Frettchen (Mustela putorius furo) und Ratten (Rattus norvegicus; Stämme Wistar und Long-Evans) Dissertation zur Erlangung des Grades eines Doktors der Naturwissenschaften der Fakultät für Biologie an der Ruhr-Universität Bochum angefertigt am Lehrstuhl für Allgemeine Zoologie und Neurobiologie vorgelegt von Daniela Hupfeld Lünen 2005 I Dissertation eingereicht am 15. 04. 2005 Betreuer: Prof. Dr. K.-P. Hoffmann Lehrstuhl für Allgemeine Zoologie & Neurobiologie Korefferent: Prof Dr. W. Kirchner AG für Verhaltensbiologie & Didaktik der Biologie Dekan: Prof. Dr. T. Stützel Lehrstuhl für Spezielle Botanik Content 1 General introduction ........................................................................................1 1.1 Albinism....................................................................................................1 1.1.1 Genotypes and phenotypes...............................................................2 1.1.2 Molecular biology of albinism ............................................................2 1.2 Effects of albinism on vision ...................................................................
Publié le : samedi 1 janvier 2005
Lecture(s) : 32
Source : WWW-BRS.UB.RUHR-UNI-BOCHUM.DE/NETAHTML/HSS/DISS/HUPFELDDANIELA/DISS.PDF
Nombre de pages : 147
Voir plus Voir moins





VViissuuaall ppeerrcceeppttiioonn ddeeffiicciittss iinn aallbbiinnoottiicc mmaammmmaallss ––
ferrets (Mustela putorius furo) and rats (Rattus
norvegicus; strains Wistar and Long-Evans)


Visuelle Wahrnehmungsdefizite albinotischer Säuger – Frettchen
(Mustela putorius furo) und Ratten (Rattus norvegicus; Stämme
Wistar und Long-Evans)




Dissertation
zur Erlangung des Grades eines
Doktors der Naturwissenschaften
der Fakultät für Biologie
an der Ruhr-Universität Bochum



angefertigt am
Lehrstuhl für Allgemeine Zoologie und Neurobiologie

vorgelegt von Daniela Hupfeld
Lünen
2005


I




















Dissertation eingereicht am 15. 04. 2005

Betreuer: Prof. Dr. K.-P. Hoffmann
Lehrstuhl für Allgemeine Zoologie & Neurobiologie

Korefferent: Prof Dr. W. Kirchner
AG für Verhaltensbiologie & Didaktik der Biologie

Dekan: Prof. Dr. T. Stützel
Lehrstuhl für Spezielle Botanik



Content
1 General introduction ........................................................................................1
1.1 Albinism....................................................................................................1
1.1.1 Genotypes and phenotypes...............................................................2
1.1.2 Molecular biology of albinism ............................................................2
1.2 Effects of albinism on vision .....................................................................4
1.2.1 Retina................................................................................................4
1.2.2 Cell gradients.....................................................................................5
1.2.3 Retinal projections to higher visual centres .......................................6
1.2.4 Stereopsis .........................................................................................9
1.3 Oculomotor reactions..............................................................................10
1.3.1 Neuronal substrate for oculomotor reactions...................................11
1.4 Visual motion perception ........................................................................12
1.5 The rat ....................................................................................................13
1.5.1 Laboratory rat strains.......................................................................13
1.5.2 Visual system of the rat ...................................................................14
1.5.3 Retina..............................................................................................14
1.5.4 Optokinetic system and behaviour...................................................15
1.5.5 Higher visual centres.......................................................................16
1.6 The ferret................................................................................................18
1.6.1 Visual system of the ferret ...............................................................18
1.6.2 Retina..............................................................................................19
1.6.3 Optokinetic system ..........................................................................20
1.6.4 Higher visual centres.......................................................................21
1.7 Aim of the study......................................................................................23
2 Visual motion perception in Wistar and Long-Evans rats...............................25
2.1 Animals...................................................................................................25
2.2 Setup ......................................................................................................25
2.3 Procedure...............................................................................................26
2.3.1 Handshaping ...................................................................................26
2.3.2 Discrimination training .....................................................................27
2.3.3 Coherence discrimination ................................................................27
2.4 Stimuli.....................................................................................................28
I 2.5 Analysis ..................................................................................................30
2.6 Results....................................................................................................31
2.6.1 Visual discrimination and coherence detection................................31
2.6.2 Coherence threshold .......................................................................32
2.7 Conclusions............................................................................................33
3 Visual motion perception in albinotic and pigmented ferrets..........................34
3.1 Animals...................................................................................................34
3.2 Setup ......................................................................................................35
3.3 Procedure...............................................................................................35
3.3.1 Handshaping ...................................................................................36
3.3.2 Discrimination training .....................................................................36
3.3.3 Coherence discrimination ................................................................37
3.4 Stimuli.....................................................................................................38
3.4.1 Training ...........................................................................................38
3.4.2 Coherence detection and threshold.................................................39
3.5 Analysis ..................................................................................................40
3.6 Results....................................................................................................41
3.6.1 Visual discrimination and coherence detection................................41
3.6.2 Coherence threshold .......................................................................42
3.7 Conclusions............................................................................................44
4 Effects of PSS lesions on visual motion perception in ferrets ........................45
4.1 Introduction.............................................................................................45
4.2 Materials and methods ...........................................................................46
4.2.1 Animals............................................................................................46
4.2.2 Stimuli..............................................................................................47
4.2.3 Prelesion training.............................................................................48
4.2.4 Measurements of the horizontal optokinetic reaction.......................49
4.2.5 Surgery............................................................................................50
4.2.6 Postlesion training ...........................................................................52
4.2.7 Analysis ...........................................................................................52
4.3 Results....................................................................................................53
4.3.1 Reconstruction of cortical lesions ....................................................53
4.3.2 Pre- and postlesion visual discrimination performance....................61
II 4.3.3 Horizontal optokinetic reaction.........................................................65
4.4 Conclusion..............................................................................................70
5 Visual acuity and contrast sensitivity of albinotic and pigmented ferrets........71
5.1 Introduction.............................................................................................71
5.1.1 Influence of dot size on coherence detection ..................................71
5.2 Materials and methods ...........................................................................72
5.2.1 Animals............................................................................................72
5.2.2 Setup and stimuli.............................................................................72
5.2.3 Procedure........................................................................................73
5.2.4 Analysis ...........................................................................................74
5.3 Results....................................................................................................74
5.3.1 Visual acuity ....................................................................................74
5.3.2 Contrast sensitivity function.............................................................75
5.4 Conclusion..............................................................................................76
6 Behavioural phenotyping of Wistar and Long-Evans rats ..............................76
6.1 Introduction.............................................................................................76
6.2 Material and methods .............................................................................77
6.2.1 Animals............................................................................................77
6.2.2 Setup...............................................................................................77
6.2.3 Procedure........................................................................................78
6.2.4 Analysis ...........................................................................................79
6.3 Results....................................................................................................80
6.4 Conclusions............................................................................................82
7 Behavioural phenotyping of albino and wildtype ferrets.................................82
7.1 Introduction.............................................................................................82
7.2 Home-cage activity of ferrets ..................................................................83
7.2.1 Animals............................................................................................83
7.2.2 Setup...............................................................................................83
7.2.3 Procedure........................................................................................83
7.2.4 Analysis ...........................................................................................84
7.2.5 Results ............................................................................................84
7.2.6 Conclusion.......................................................................................84
7.3 Activity and object recognition in open field tasks...................................85
III 7.3.1 Animals............................................................................................85
7.3.2 Setup, procedure and analysis ........................................................85
7.3.3 Results ............................................................................................86
7.3.4 Conclusions.....................................................................................87
8 Postnatal optokinetic reactions in albinotic and pigmented ferrets.................88
8.1 Introduction.............................................................................................88
8.2 Animals...................................................................................................89
8.3 Setup ......................................................................................................89
8.4 Procedure...............................................................................................90
8.5 Analysis ..................................................................................................90
8.6 Results....................................................................................................91
8.7 Conclusion..............................................................................................94
9 Discussion .....................................................................................................95
9.1 Animal models ........................................................................................95
9.2 Methods..................................................................................................96
9.3 Motion perception and cortical representation of motion ........................98
9.4 Visual acuity and contrast sensitivity ....................................................103
9.5 Behavioural phenotyping ......................................................................108
9.6 Optokinetic reactions in ferret pups ......................................................114
10 Summary..................................................................................................115
11 Zusammenfassung...................................................................................117
12 References...............................................................................................120

IV
Tables
Table 1: Ferrets used in global motion perception tasks.......................................34
Table 2: Ferrets used for lesion experiments........................................................47
Table 3: Cortical areas affected by lesions ...........................................................61
Table 4: Qualitative summary of post-lesion performance....................................65
Table 5: Qualitative summary of post-lesion horizontal optokinetic reactions.......69
Table 6: Ferrets used for visual acuity and contrast sensitivity experiments.........72
Table 7: Contrast of stimuli for contrast-sensitivity tests .......................................73
Table 8: Recording sessions in ferret pups, post-eye-opening day 0-10 ..............91


Abbreviations
ALB albino
ANOVA analysis of variance
ant anterior
ccw counter-clockwise
Cm Michelson contrast
cpd cycles per degree
cw clockwise
dor dorsal
deg; ° degree (of visual angle)
DTN dorsal terminal nucleus of the optic tract
EOG electro-oculogramme
Fig figure
fMRI functional Magnet-Resonanz-Imaging
GC ganglion cell
Hz Hertz, 1/s
i. m. intramuscular
L left
LE Long-Evans rat
ls lateral sulcus
LTN lateral terminal nucleus of the optic tract
lum luminance
V max maximal
min minimal
MST medio superior temporal area
MT medio temporal area
MTN medial terminal nucleus of the optic trakt
NT nasotemporal
NOT nucleus of the optic tract
OKN optokinetic nystagmus
OKR optokinetic reaction
OMR optomotoric reaction
PMLS posterior medio lateral suprasylvian (cortex)
ps pseudosylvian sulcus
PSS posterior suprasylvian cortex
R right
REM rapid eye movement
RDP random dot pattern
RPE retinal pigment epithelium
s second
SC superior colliculus
ss suprasylvian sulcus
st. dev. standard deviation
TH tyrosine-hydroxylase
TN temporonasal
Tyr tyrosinase
v. a. visual angle
V1 Visual area 1
V2 Visual area 2
V3 Visual area 3
V5 Visual area 5
VOR vestibulo ocular reflex
WIS Wistar rat
WT wildtype

VI 1 General introduction
1 General introduction
The evolution of vision, like other sensory modalities, improved the reproductive
fitness of the animal. Besides the detection of light and dark the detection and
identification of obstacles and whether and in which direction they move is very
important. Vision is essential for most vertebrates to orient and navigate in the
environment, to detect potential prey or predators as well as to perceive signals in
social communication.

One approach to investigate the function, development or plasticity of the visual
system is the targeted deletion of certain input. Visual information from the retina
can be removed for example by dark-rearing, enucleation, masking or lid-suture.
Cortical input can be deleted by pharmacological blocking, cooling or lesioning of
certain parts of the cortex. All these manipulation are applied postnatally. Opposed
to this an inherited deficit of the visual system development is present in
hypopigmented animals. Albino animals are therefore a valuable model for basic
visual research. What are the consequences of albinism for the central visual
system and for visually guided behaviour? One of the deficits of the mammalian
albino visual system concerns the optokinetic response. Albino ferrets and albino
Wistar rats don´t perform a regular optokinetic nystagmus, which is an important
finding because it cannot be explained on the basis of the known albino specific
deficits in these species, as summarized below.

1.1 Albinism
Albinism is a disorder of melanin synthesis, genetically determined but
heterogeneous. The term albino refers to a specific phenotype characterised by
the lack of melanin in all parts of the body (skin, fur or feathers) and the eyes (iris,
retinal pigment epithelium). For most species this leads to a remarkable
appearance - albinotic individuals appear mostly “white” and seem to have “red”
eyes. This phenomenon can be found throughout the animal kingdom, including all
vertebrate classes where it is rare but present also in feral animals.

- 1 - 1 General introduction
In some forms albinism does not necessarily lead to the red eye phenomenon,
instead subjects (humans as well as animals like horses, cats, dogs) have light
blue irides. Some residual pigmentation of the stroma or posterior epithelium
seems to lead to this appearance.

1.1.1 Genotypes and phenotypes
Several types of albinism can be distinguished in human patients (for review see
Lyle, Sangster & Williams 1997) with different genes being affected by various
mutations (for review see Oetting 1999, Oetting & King 1999). The key enzyme in
melanin formation is tyrosinase and is most often affected by mutations leading to
the albino appearance. The gene coding tyrosinase (TYR) has been found on e. g.
chromosome 11 in humans and on chromosome 7 in mice (Barton, Kwon &
Francke 1988, for review see Searle 1990). Even though the tyr-gene seems to be
highly conserved the flanking regions differ markedly.

A complete lack of pigmentation of eyes and body throughout life characterises the
oculocutaneous albinism OCA in humans, the ocular albinism OA is the next
numerous type in humans. Albino mammals used in this study show a form of
complete (tyrosinase-negative) albinism comparable to human OCA. A form of
albinism less obvious is the temperature sensitive variation called “siamese” in
cats and “himalayan” in hamsters, mice and rabbits. In this type of albinism
pigment is only synthesied in relatively cold parts of the body (paws, tail, ears) but
not in the eye. This type can also occur in humans (King et al. 1991). As far as the
visual system is concerned all these genetically distinct genotypes lead to the
same phenotype concerning the retinal pigment epithelium pigmentation is
affected (see 1.1.2).

1.1.2 Molecular biology of albinism
The first steps in melanin synthesis depend on tyrosinase (see Figure 1), which
catalyses the formation of L-Dopa (3,4-dihydroxyphenylalanine) from tyrosine (e. g.
Cooksey et al. 1997) in melanocytes. Tyrosinase catalyses the conversion from L-
Dopa to dopaquinone, which is further processed to finally build red to yellow
phaeo- and brown to black eumelanin.
- 2 -

Soyez le premier à déposer un commentaire !

17/1000 caractères maximum.