Authors BioNB 4240 Discussion: Aug. 31, 2011 Carl D Hopkins Carl D. - - PDF document

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BioNB 4240 Discussion: Aug. 31, 2011 Carl D Hopkins Carl D. Hopkins

Review of Jon H Kaas and Ken Catania’s (2002) review paper: How do features of sensory representations develop?. BioEssays 24.4:334‐ 343.

Authors

• Dr. Jon Kaas

Distinguished Centennial Professor of Psychology Associate Professor of Cell and Developmental Biology Professor of Radiology and Radiological Sciences Vanderbilt University Nashville, Tennessee Kenneth C. Catania , Ph.D. Professor of Biological Sciences Stevenson Professor of Biological Sciences

• Dept. Biology

Vanderbilt University

Jon Kaas

• Education
• B.A., Northland College, Ashland, Wisconsin,

Psychology, 1959 Ph D Psychology Duke University 1965 Ph.D., Psychology, Duke University, 1965 ‐ Thesis Advisor: I.T. Diamond Postdoctoral Fellow, Neurophysiology, University of Wisconsin, 1965‐1968 ‐ Sponsor: C.N. Woolsey

Ken Catania

• Catania received a BS in zoology from the University of
• Maryland. In 1992, he received an MS in Neurosciences from

the University of California, San Diego (with Glenn Northcutt), followed in 1994 with a Ph.D. from UCSD. Catania was a post doctoral fellow at Vanderbilt from 1995‐1997 (with Jon Kaas). ( ) In 2000 Catania became an assistant professor at Vanderbilt.

• MacArthur Genius Award (2006)

The Journal

BioEssays (Jon Wiley and Sons, Inc) [Wiley‐Blackwell] IMPACT FACTOR = 4.479 A = the number of times articles published in 2006 and 2007 were cited by indexed journals during 2008. B = the total number of "citable items" published by that journal in 2006 and 2007. ("Citable items" are usually articles, reviews, proceedings, or notes; not editorials or Letters‐to‐ the‐Editor.) 2008 impact factor = A/B.

• molecular – cellular – biomedical – physiology – translational research – systems ‐ hypotheses encouraged
• BioEssays is a review‐and‐discussion journal publishing novel insights, forward‐

looking reviews and commentaries in contemporary biology with a molecular, genetic, cellular, or physiological dimension. A further aim is to emphasise transdisciplinarity and integrative biology in the context of

• rganismal studies, systems approaches, through to ecosystems where
• appropriate. The journal has three main sections: Insights & Perspectives (for

ideas, hypotheses and commentaries), Prospects & Overviews (for review‐style articles) and Reports & Opinion (for meeting reports, book reviews and letters to the Editor). The Prospects & Overviews section contains mini‐reviews highlighting very recent research articles, and longer papers that present a field, its developments and prospects for a broad readership; we also welcome methods papers (including presentation of new model systems) under the rubric Methods, Models & Techniques. The journal's insightful analysis makes it essential reading for professional researchers (from basic research through to medically‐related fields), as well as an invaluable tool for lecturers and students.

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Mammalian Cortex

Two pathways from skin to Cortex

In vision, touch, and propioception, and hearing the sensory surface is “mapped” isomorphically onto the brainstem, the thalamus, and the cortex. How is order maintained in the maps?

• Fig. 1 Kaas and Catania (2002)

Sperry’s Idea: Chemospecificity

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Hubel and Wiesel: neuron firing determines connections.

Experiments with occular dominance columns in cortex.

• Sensory areas with activated in synchrony tend to wire up

together.

• (Experiments with artificial stimulation, or TTX application result in modified

sensory maps.)

Probably both factors are important: chemical gradients + activity patterns.

Although some experiments question the importance of activity patterns. For example, applying TTX to cortex during development of sensory map fails to disrupt the barrel cortex map of vibrissae. Postnatal blockade of cortical activity by tetrodotoxin does not disrupt the f ti f ib i l t d tt i th t' t t formation of vibrissa-related patterns in the rat's somatosensory cortex. Chiaia NL, Fish SE, Bauer WR, Bennett-Clarke CA, Rhoades RW.

Brain Res Dev Brain Res. 1992 Apr 24;66(2):244-50. PMID: 1318800 [PubMed - indexed for MEDLINE] Related citations

Examples of variation in strict somatotopy in somatosensory cortex

• Tree shrew: dorsal trunk maps medial to the

hindlimb instead of lateral, as in most mammals.

• Primates: arm to hand map is reversed in
• Primates: arm to hand map is reversed in

gallago compared to all other primtes.

• S1 cortex maps the “hand” of bats in reverse
• rder compared to other mammals

Variation in Retinal Maps

• Primates: each cortex represents contralateral

hemifield, but many species receive significant ipsilateral hemifield projections.

• Activity patterns may contribute to these
• Activity patterns may contribute to these

species differences.

Modular and Laminar maps are variable across species

• On and off ganglion cells from retina segregate

into different layers in LGN in tree shrews, and different sublayers in cortex same layers in other mammals.

• Large variation in degree of ODCs in mammals

Large variation in degree of ODCs in mammals.

• Modalities mix or segregate in different species:

Platypus: electroreception segregated from tactile senses. Monkeys: segregate RA and SA mechanoreceptors; rats and mice do not.

• Thus, it appears that activity dependent

development is of variable importance.

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Septa appear in maps formed from discrete sensory units (whiskers, digits)

Cytochrome oxidase levels high (activity) low (low activity) Barrel Cortex

Star Nose Mole Mechanoreceptors also projects into a modular map in S1

• Star nose mole
• Scanning EM of one half
• Scanning EM of one half
• f star
• S1 cortex. Cytochrome
• xidase stain.

Septa occur in the S2 map of the forepaw of the mole

• Star nose mole forepaw
• CO activity in S2

Septa occur only in sensory maps with disruptions of sensory surface

• between pads on paw
• between hand and face when juxtaposed
• between lips, teeth, tongue
• in LGN where optic disk disrupts retina
• Septa also occur in visual system between discorrelated

receptor types: e.g. laminae in LGN representing differing cell types (Parvo‐cellular, magnocellular and contra‐ versus ipsilateral eye)

• Septa are absent in auditory cortex which receives

continuously varying tonotopic input from cochlea.

In rare cases of extra sensory lobes; extra modules exist in brainstem, thalamus, and cortex. Correlated activity induces module in three sensory structures. Siamese cats have nearly completely crossed optic nerves (complete decussation), unlike normal cats which have partial decussation. In turn, the contralateral projection of A1 is inverted, maintaining continuity with the normal projection of the ipsilateral retina. Likely that activity patterns determine the orientation of the inverted map.

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Conclusion

1) gradients of signaling molecules produced in sensory surfaces appear to be important in establishing crude maps of sensory surfaces in the brain. 2) Information received from the receptor sheet seems to control the fine structure of the maps – modular control the fine structure of the maps modular elements. 3) Evidence comes from experimental manipulations of sensory surfaces (additional whisker or lobe of star) alters map devepopment. 4) Variation in map structure across species appears to be largely determined by activity patterns.

New optical methods reveal feature specific substructure within each barrel related to the direction of vibrissa motion, which appears only in adults. Suggests also that activity dependent information influences the map structure in the adult.

Yves Kremer, Jean‐François Léger, Dan Goodman, Romain Brette, and Laurent

• Bourdieu. (2011) Late Emergence of the Vibrissa Direction Selectivity Map in the

Rat Barrel Cortex. The Journal of Neuroscience, July 20, 2011 • 31(29):10689 – 10700 • 10689