Finlay, BL, Darlington, RB, Nicastro N: Developmental structure in brain evolution
BBS 24(2) xxxxxx preprint

"encephalization qutient":
brain size is correlated with body size: e.g. ruby-throated hummingbird (brain less than 1 gramm) vs baleen whale (brain in excess of 50000 gramms) -  both sing, defend territories and mates, raise young and migrate seasonally.
specialized sense-organs arre also correlated in size with body size

Why are not basic mechanisms of action, memory, communication and cognition scale-independent?

What does it mean exactly to grow bigger brains?  Do some areas get relatively bigger or the whole brain just gets bigger?
 

Differential contributions of magnocellular and parvocellular pathways to the contrast response of neurons in bush baby primary visual cortex (V1).  Vis Neurosci 2000 Jan-Feb;17(1):71-6

Allison JD, Melzer P, Ding Y, Bonds AB, Casagrande VA.

Department of Cell Biology, Vanderbilt University, Nashville, TN 37232-2175, USA.

How neurons in the primary visual cortex (V1) of primates process parallel inputs from the magnocellular (M) and parvocellular (P) layers of the lateral geniculate nucleus (LGN) is not completely understood. To investigate whether signals from the two pathways are integrated in the cortex, we recorded contrast-response functions (CRFs) from 20 bush baby V1 neurons before, during, and after pharmacologically inactivating neural activity in either the contralateral LGN M or P layers. Inactivating the M layer reduced the responses of V1 neurons (n = 10) to all stimulus contrasts and significantly elevated (t = 8.15, P < 0.01) their average contrast threshold from 8.04 (+/- 4.1)% contrast to 22.46 (+/- 6.28)% contrast. M layer inactivation also significantly reduced (t = 4.06, P < 0.01) the average peak response amplitude. Inactivating the P layer did not elevate the average contrast threshold of V1 neurons (n = 10), but significantly reduced (t = 4.34, P < 0.01) their average peak response amplitude. These data demonstrate that input from the M pathway can account for the responses of V1 neurons to low stimulus contrasts and also contributes to responses to high stimulus contrasts. The P pathway appears to influence mainly the responses of V1 neurons to high stimulus contrasts. None of the cells in our sample, which included cells in all output layers of V1, appeared to receive input from only one pathway. These findings support the view that many V1 neurons integrate information about stimulus contrast carried by the LGN M and P pathways.
 
 
 

Disparity tuning in macaque area V4.

Hinkle DA, Connor CE.   Neuroreport 2001 Feb 12,;12(2):365-9

Department of Neuroscience, Johns Hopkins University School of Medicine and Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore MD 21218, USA.

Neural processing of stereoscopic depth is conventionally associated with the dorsal (spatial) pathway in primate visual cortex. The role of depth information in the ventral (object) pathway has been less certain. We found prominent tuning for stereoscopic disparity in area V4, an intermediate stage in the ventral pathway. Eighty percent of the cells in our sample exhibited significant disparity tuning over the -1.0 degree to 1.0 degree range, and the majority showed > 2:1 response differences. Tuning function shapes were similar to those reported previously in other visual areas. We observed a significant tuning bias towards crossed (near) disparities. This could reflect an emphasis in the ventral pathway on foreground objects or parts of objects projecting towards the viewer.

 Curr Biol 2000 Jan 13;10(1):35-8

The human visual system is optimised for processing the spatial information in natural visual images.

Parraga CA, Troscianko T, Tolhurst DJ.

Department of Experimental Psychology, Bristol University, UK. Alej.Parraga@bris.ac.uk

A fundamental tenet of visual science is that the detailed properties of visual systems are not capricious accidents, but are closely matched by evolution and neonatal experience to the environments and lifestyles in which those visual systems must work. This has been shown most convincingly for fish and insects. For mammalian vision, however, this tenet is based more upon theoretical arguments than upon direct observations. Here, we describe experiments that require human observers to discriminate between pictures of slightly different faces or objects. These are produced by a morphing technique that allows small, quantifiable changes to be made in the stimulus images. The independent variable is designed to give increasing deviation from natural visual scenes, and is a measure of the Fourier composition of the image (its second-order statistics). Performance in these tests was best when the pictures had natural second-order spatial statistics, and degraded when the images were made less natural. Furthermore, performance can be explained with a simple model of contrast coding, based upon the properties of simple cells in the mammalian visual cortex. The findings thus provide direct empirical support for the notion that human spatial vision is optimised to the second-order statistics of the optical environment.
 

Proc R Soc Lond B Biol Sci 1997 Sep 22;264(1386):1303-7
Visual and socio-cognitive information processing in primate brain evolution.

Joffe TH, Dunbar RI.

School of Life Sciences, University of Liverpool, UK.

Social group size has been shown to correlate with neocortex size in primates. Here we use comparative analyses to show that social group size is independently correlated with the size of non-V1 neocortical areas, but not with other more proximate components of the visual system or with brain systems associated with emotional cueing (e.g. the amygdala). We argue that visual brain components serve as a social information 'input device' for socio-visual stimuli such as facial expressions, bodily gestures and visual status markers, while the non-visual neocortex serves as a 'processing device' whereby these social cues are encoded, interpreted and associated with stored information. However, the second appears to have greater overall importance because the size of the V1 visual area appears to reach an asymptotic size beyond which visual acuity and pattern recognition may not improve significantly. This is especially true of the great ape clade (including humans), that is known to use more sophisticated social cognitive strategies.

Philos Trans R Soc Lond B Biol Sci 2000 Sep 29;355(1401):1239-42 Environmental factors which may have led to the appearance of colour vision.
Maximov VV.

Institute for Problems of Information Transmission, Russian Academy of Sciences, Moscow. maximov@iitp.ru

It is hypothesized that colour vision and opponent processing of colour signals in the visual system evolved as a means of overcoming the extremely unfavourable lighting conditions in the natural environment of early vertebrates. The significant flicker of illumination inherent in the shallow-water environment complicated the visual process in the achromatic case, in particular preventing early detection of enemies. The presence of two spectral classes of photoreceptors and opponent interaction of their signals at a subsequent retinal level allowed elimination of the flicker from the retinal image. This new visual function provided certain advantages concerning reaction times and favoured survival. This assumption explains why the building blocks for colour vision arose so early, i.e. just after the active predatory lifestyle was mastered. The principal functions of colour vision inherent in extant animals required a more complex neural machinery for colour processing and evolved later as the result of a change in visual function favouring colour vision.
 
 

Shimizu, Toru; Bowers, Alexia N.
Title Visual circuits of the avian telencephalon: Evolutionary
implications.
Source Behavioural Brain Research. Vol 98(2) Feb 1999, 183-191.

Abstract: Birds and primates are vertebrates that possess the most
advanced, efficient visual systems. Although lineages leading to these two
classes were separated about 300 million years ago, there are striking
similarities in their underlying neural mechanisms for visual
processing. This paper discusses such similarities with special emphasis
on the visual circuits in the avian telencephalon. These similarities
include: (1) the existence of two parallel visual pathways and their
distinct telencephalic targets, (2) anatomical and functional segregation
within the visual pathways, (3) laminar organization of the telencephalic
targets of the pathways (e.g. striate cortex in primates), and
(4) possible interactions between multiple visual areas. Additional
extensive analyses are necessary to determine whether these similarities
are due to inheritance from a common ancestral stock or the consequences
of convergent evolution based on adaptive response to similar selective
pressures. Nevertheless, such a comparison is important to identify the
general and specific principles of visual processing in amniotes
(reptiles, birds, and mammals). Furthermore, these principles in turn will
provide a critical foundation for understanding the evolution of the brain
in amniotes.

Rosa, Marcello G. P. and Krubitzer, Leah A.
The evolution of visual cortex: where is V2?
Trends in Neurosciences
Volume 22, Issue 6
1 June 1999
Pages 242-248
Abstract: A comparative analysis of the area of the cortex that is
adjacent to the primary visual area (V1), indicates that the lateral
extrastriate cortex of primitive mammals was likely to contain only a
single visuotopically organized field, the second visual area (V2). Few,
if any, other visual areas existed. The opposing hypothesis, that
primitive mammals had a `string' of small visual areas in the cortex
lateral to V1 (as in some rodents), is not supported by studies of the
organization of extrastriate cortex in other mammals, nor by the
variability in this organization among extant rodents. A critical
re-analysis of published evidence on the presence of multiple areas
adjacent to V1 in some rodents has led to alternative interpretations of
the organization of the areas in these regions.

Sara Cordes

Behav Brain Res 1999 Feb 1;98(2):183-91
Title:  Visual circuits of the avian telencephalon: evolutionary implications.
Authors:  Shimizu T, Bowers AN. Department of Psychology, University of South Florida, Tampa 33620, USA. shimizu@chuma.cas.usf.edu
Abstract:  Birds and primates are vertebrates that possess the most advanced, efficient visual systems. Although lineages leading to these two classes were separated about 300 million years ago, there are striking similarities in their underlying neural mechanisms for visual processing. This paper discusses such similarities with special emphasis on the visual circuits in the avian telencephalon. These similarities include: (1) the existence of two parallel visual pathways and their distinct telencephalic targets, (2) anatomical and functional segregation within the visual pathways, (3) laminar organization of the telencephalic targets of the pathways (e.g. striate cortex in primates), and (4) possible interactions between multiple visual areas. Additional extensive analyses are necessary to determine whether these similarities are due to inheritance from a common ancestral stock or the consequences of convergent evolution based on adaptive response to similar selective pressures. Nevertheless, such a comparison is important to identify the general and specific principles of visual processing in amniotes (reptiles, birds, and mammals). Furthermore, these principles in turn will provide a critical foundation for understanding the evolution of the brain in amniotes.
 

Proc Natl Acad Sci U S A 1991 Mar 1;88(5):1621-5
Title:  Dissociation of object and spatial visual processing pathways in human extrastriate cortex.
Authors:  Haxby JV, Grady CL, Horwitz B, Ungerleider LG, Mishkin M, Carson RE, Herscovitch P, Schapiro MB, Rapoport SI. Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892.
Abstract:  The existence and neuroanatomical locations of separate extrastriate visual pathways for object recognition and spatial localization were investigated in healthy young men. Regional cerebral blood flow was measured by positron emission tomography and bolus injections of H2(15)O, while subjects performed face matching, dot-location matching, or sensorimotor control tasks. Both visual matching tasks activated lateral occipital cortex. Face discrimination alone activated a region of occipitotemporal cortex that was anterior and inferior to the occipital area activated by both tasks. The spatial location task alone activated a region of lateral superior parietal cortex. Perisylvian and anterior temporal cortices were not activated by either task. These results demonstrate the existence of three functionally dissociable regions of human visual extrastriate cortex. The ventral and dorsal locations of the regions specialized for object recognition and spatial localization, respectively, suggest some homology between human and nonhuman primate extrastriate cortex, with displacement in human brain, possibly related to the evolution of phylogenetically newer cortical areas.

Accession Number
  Dissertation Abstract:  1999-95002-473.
Author
  Smith, Elliott Grainger.
Title
  Predictive saccadic eye movements and visual expectations in two-month-old infants: Implications for neuroanatomical theories of attention, maturation of visual pathways, and development of prefrontal cortex.
Source
  Dissertation Abstracts International: Section B: the Sciences & Engineering. Vol 59(7-B), Jan 1999, 3741, US: Univ. Microfilms International.
Abstract
  Prefrontal cortex is critically involved in sustaining representations across temporal gaps in the perception-action cycle. Historically, it has been believed that representations of the sort mediated by prefrontal cortex are unavailable to newborns or young infants. Indeed, existing developmental theories of visual attention have considered newborns to be predominantly decorticate creatures who do not attain functional maturity in the frontal lobes until about 4 to 6 months of age. However, research using the visual expectation procedure has revealed frontally-mediated predictive saccadic eye movements in 2-month-old infants. The purpose of the present experiment was to test an alternative theory, the dual-streams model, which seeks to explain under what conditions predictive saccades are observed in 2-month-old infants. According to the model, prefrontal structures known as the frontal eye fields are able to trigger predictive saccades in response to cross-temporal contingencies relying on the processing of spatiotemporal information before they trigger predictive saccades in response to featural contingencies. The mechanism for the different times of emergence is differential maturation in the dorsal and ventral visual streams of processing. Two-month-old infants were given two predictive saccade tasks, the color task and the flicker task, on separate days within one week. Success on the color task required featural processing within the ventral visual stream, while success on the flicker task required spatiotemporal processing within the dorsal stream. Trials within the tasks involved presenting a central cue for 2 s that was either red or blue in the color task or blinking or static in the flicker task. After a 1 s delay, which provided the opportunity for predictive saccades, a peripheral target appeared either to the left or right. Location of the target was contingent upon the identity of the cue. The proportion of correct predictive saccades was measured. In accord with expectations, 2-month-olds detected the blinking-cue/left-target contingency in the flicker task, but neither of the contingencies in the color task.

Elias Cohen

Prog Brain Res  2001;134:285-95

Visual cortex organization in primates: theories of V3 and adjoining
visual areas.

Kaas JH, Lyon DC.

Department of Psychology, 301 Wilson Hall, Vanderbilt University, 111 21st
Avenue South, Nashville, TN 37203, USA. jon.kaas@vanderbilt.edu

After years of experimentation and substantial progress, there is still
only limited agreement on how visual cortex in primates is organized, and
what features of this organization are variable or stable across lines of
primate phylogeny. Only three visual areas, V1, V2, and MT, are widely
recognized as common to all primates, although there are certainly more. Here we
consider various concepts of how the cortex along the outer border of V2 is
organized. An early proposal was that this region is occupied by a V3 that is as wide
and as long as V2, and represents the visual hemifield as a mirror image of V2.
We refer to this notion as the classical V3 or V3-C. Another proposal is
that only the dorsal half of V3-C exists, the half representing the lower visual
quadrant, and thus the representation is incomplete (V3-I) by half. A version of
this proposal is that V3-I is discontinuous, extremely thin in places, and
highly variable across individuals, much as a vestigial or degenerate structure
might be (V3-IF-incomplete and fragmented). A fourth proposal is that there is
no V3. Many results suggest that a series of visual areas border V2, none of
which has the characteristics of V3. Alternatively, the possibility exists that
primate taxa differ with regard to visual areas bordering V2. Currently, much of
the supporting evidence for a classical V3 comes from fMRI studies in
humans, much of the evidence for a series of bordering areas comes from New World
Monkeys and prosimian galagos, and much of the evidence for a V3-I or V3-IF comes
from macaque monkeys. Possibly all these interpretations of visual cortex
organization are valid, but each for only one of the major groups of
primate evolution. Here, we suggest that none of these interpretations is
correct, and propose instead that a modified V3 (V3-M) exists in a similar form in
all primates. This V3-M is smaller and thinner than V3-C, discontinuous in
the middle, but with comparable dorsal and ventral halves representing the
lower and upper visual hemifields, respectively. Because the evidence for V3-M is
limited, and it stems in part from our ongoing but incomplete comparative studies
of V1 connections in primates, this suggestion requires further experimental
evaluation and it remains tentative.
 

Perception of Fourier and non-Fourier motion by larval zebrafish

Orger, M B; Smear, M C; Anstis, S M; Baier, H

Department of Physiology and Program in Neuroscience, University of
California at San Francisco, Box 0444, Room S762, 513, Parnassus, San
Francisco,
California 94143-0444, USA

Abstract

A moving grating elicits innate optomotor behavior in zebrafish larvae;
they swim in the direction of perceived motion. We took advantage of
this behavior, using computer-animated displays, to determine what attributes of motion are
extracted by the fish visual system. As in humans, first-order
(luminance-defined or Fourier) signals dominated motion perception in fish; edges or other
features had little or no effect when presented with these signals.
Humans can see complex movements that lack first-order cues, an ability that is usually
ascribed to higher-level processing in the visual cortex. Here we show
that second-order (non-Fourier) motion displays induced optomotor behavior in zebrafish
larvae, which do not have a cortex. We suggest that second-order motion
is extracted early in the lower vertebrate visual pathway.

Preuss TM, Qi H, Kaas JH.
Distinctive compartmental organization of human primary visual cortex.
Proc Natl Acad Sci U S A. 1999 Sep 28;96(20):11601-6.
PMID: 10500223 [PubMed - indexed for MEDLINE]
In the primary visual area of macaques and other monkeys, layer 4A is a mosaic of separate tissue compartments related to the parvocellular (P) and magnocellular (M) layers of the lateral geniculate nucleus. This mosaic resembles a honeycomb, with thin walls that receive direct P inputs and cores consisting of columns of dendrites and cell bodies ascending from layer 4B, a layer that receives indirect M inputs. To determine whether apes and humans have a macaque-like layer 4A, we examined the primary visual area in humans, chimpanzees, an orangutan, Old World monkeys, and New World monkeys. Apes and humans lacked the dense band of cytochrome oxidase staining in layer 4A that marks the stratum of P-geniculate afferents in monkeys. Furthermore, humans displayed a unique arrangement of presumed M-related cells and dendrites in layer 4A, as revealed with antibodies against nonphosphorylated neurofilaments and microtubule-associated protein 2. Human 4A contained a large amount of M-like tissue distributed in a complex, mesh-like pattern rather than in simple vertical arrays as in other anthropoid primates. Our results suggest that (i) the direct P-geniculate projection to layer 4A was reduced early in the evolution of the ape-human group, (ii) the M component of layer 4A was subsequently modified (and possibly enhanced) in the human lineage, and (iii) the honeycomb model does not adequately characterize human layer 4A. This is the first demonstration of a difference in the cortical architecture of humans and apes, the animals most closely related to humans.
 

Striedter GF, Northcutt RG.
Two distinct visual pathways through the superficial pretectum in a percomorph
teleost.
J Comp Neurol. 1989 May 15;283(3):342-54.
PMID: 2745744 [PubMed - indexed for MEDLINE]
 

Lee BB, Silveira LC, Yamada ES, Hunt DM, Kremers J, Martin PR, Troy JB, da
Silva-Filho M.
Visual responses of ganglion cells of a New-World primate, the capuchin monkey, Cebus apella.
J Physiol. 2000 Nov 1;528(Pt 3):573-90.
PMID: 11432364 [PubMed - indexed for MEDLINE]
1. The genetic basis of colour vision in New-World primates differs from that in humans and other Old-World primates. Most New-World primate species show a polymorphism; all males are dichromats and most females trichromats. 2. In the retina of Old-World primates such as the macaque, the physiological correlates of trichromacy are well established. Comparison of the retinae in New- and Old-World species may help constrain hypotheses as to the evolution of colour vision and the pathways associated with it. 3. Ganglion cell behaviour was recorded from trichromatic and dichromatic members of a New-World species (the capuchin monkey, Cebus apella) and compared with macaque data. Despite some differences in quantitative detail (such as a temporal response extended to higher frequencies), results from trichromatic animals strongly resembled those from the macaque. 4. In particular, cells of the parvocellular (PC) pathway showed characteristic frequency-dependent changes in responsivity to luminance and chromatic modulation, cells of the magnocellular (MC) pathway showed frequency-doubled responses to chromatic modulation, and the surround of MC cells received a chromatic input revealed on changing the phase of heterochromatically modulated lights. 5. Ganglion cells of dichromats were colour-blind versions of those of trichromats. 6. This strong physiological homology is consistent with a common origin of trichromacy in New- and Old-World monkeys; in the New-World primate the presence of two pigments in the middle-to-long wavelength range permits full expression of the retinal mechanisms of trichromatic vision.
 

Barton, RA
TI Visual specialization and brain evolution in primates
SO PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES B-BIOLOGICAL
   SCIENCES
DE brain size; primates; vision; parvocellular; frugivory; social
   cognition

AB Several theories have been proposed to explain the evolution of
   species differences in brain size, but no concensus has
   emerged. One unresolved question is whether brain size
   differences are a result of neural specializations or of
   biological constraints affecting the whole brain. Here I show
   that, among primates, brain size variation is associated with
   visual specialization. Primates with large brains for their
   body size have relatively expanded visual brain areas,
   including the primary visual cortex and lateral geniculate
   nucleus. Within the visual system, it is, in particular, one
   functionally specialized pathway upon which selection has
   acted: evolutionary changes in the number of neurons in
   parvocellular, but not magnocellular, layers of the lateral
   geniculate nucleus are correlated with changes in both brain
   size and ecological variables (diet and social group size).
   Given the known functions of the parvocellular pathway, these
   results suggest that the relatively large brains of frugivorous
   species are products of selection on the ability to perceive
   and select fruits using specific visual cues such as colour.
   The separate correlation between group size and visual brain
   evolution, on the other hand, may indicate the visual basis of
   social information processing in the primate brain.

Eur J Morphol 1997 Oct;35(4):277-89
 Separate channels for visuomotor transformations in the pigeon.
Jager R.
University of Konstanz, FRG. ralf.jaeger@uni-konstanz.de

Since the discovery of two parallel visual systems in humans and primates there has been much speculation about their functions. One prominent current model, suggesting independent processing of visual information for perception and action, is supported by neuroanatomical, electrophysiological, neurobehavioral, and human clinical data. Furthermore, studies of visuomotor behavior in amphibians and non-primate mammals indicate that neural processing of action-related behavior is mediated by separate neuronal channels thus suggesting an evolutionary principle in the organization of visuomotor behavior. If such an evolutionary principle operates it should also apply to birds. I will present and discuss behavioral and behavioral physiological evidence that action-related behavior in pigeons like pecking, grasping and control of gaze is controlled via separate neuronal channels subserving visuomotor functions.
 

Behav Brain Res 1999 Feb 1;98(2):183-91
Visual circuits of the avian telencephalon: evolutionary implications.
Shimizu T, Bowers AN.

Birds and primates are vertebrates that possess the most advanced, efficient visual systems. Although lineages leading to these two classes were separated about 300 million years ago, there are striking similarities in their underlying neural mechanisms for visual processing. This paper discusses such similarities with special emphasis on the visual circuits in the avian telencephalon. These similarities include: (1) the existence of two parallel visual pathways and their distinct telencephalic targets, (2) anatomical and functional segregation within the visual pathways, (3) laminar organization of the telencephalic targets of the pathways (e.g. striate cortex in primates), and (4) possible interactions between multiple visual areas. Additional extensive analyses are necessary to determine whether these similarities are due to inheritance from a common ancestral stock or the consequences of convergent evolution based on adaptive response to similar selective pressures. Nevertheless, such a comparison is important to identify the general and specific principles of visual processing in amniotes (reptiles, birds, and mammals). Furthermore, these principles in turn will provide a critical foundation for understanding the evolution of the brain in amniotes.
 
 

               Comparative perspectives on multiple cortical visual systems.
                  Neurosci Biobehav Rev 1998 Mar;22(2):173-80
                  Ellard CG.

                  Department of Psychology, University of Waterloo, Ontario, Canada.

                  This paper argues that any effort to extend theories of cortical visual systems based on primates to other orders, such as
                  Rodentia, must take into account fundamental differences in visual system properties, such as retinal organization. Some
                  examples are given of the effects of these differences, describing several studies using gerbils in which problems in
                  object recognition appear to be solved using unique methods based on navigational information. I conclude by suggesting
                  that closer consideration of comparative issues in visual cortical processing might lead to new insights regarding the
                  evolutionary origins of object recognition as it is understood in humans and other primates, and I suggest that these
                  evolutionary antecedents might help to explain the apparent linkage in humans between object recognition and movement.
                    Zsuzsa

                  Vision, Touch and Hearing Research Centre, Dept of Physiology and Pharmacology, The University of Queensland, QLD
                  4072, Australia.

                  A comparative analysis of the area of the cortex that is adjacent to the primary visual area (V1), indicates that the lateral
                  extrastriate cortex of primitive mammals was likely to contain only a single visuotopically organized field, the second
                  visual area (V2). Few, if any, other visual areas existed. The opposing hypothesis, that primitive mammals had a 'string'
                  of small visual areas in the cortex lateral to V1 (as in some rodents), is not supported by studies of the organization of
                  extrastriate cortex in other mammals, nor by the variability in this organization among extant rodents. A critical
                  re-analysis of published evidence on the presence of multiple areas adjacent to V1 in some rodents has led to alternative
                  interpretations of the organization of the areas in these regions.
                    Suncica

On phylogenetic inferences in general:
What comparative studies of neocortex tell us about the human brain.
Rev Bras Biol. 1996 Dec;56 Su 1 Pt 2:315-22. Review.
Kaas JH.
 

There are several ways in which comparative studies of brain organization and function can be informative in attempts to understand the human brain. Often investigators study a favorable and sometimes specialized species in order to reveal features that may reflect general or widespread principles. The example used here is that the cortical representation of the unique and highly specialized receptor sheet of the nose of the star-nosed mole provides further evidence that the receptor sheet instructs the development of cortex. Comparative studies are also used to reconstruct the evolution of brain systems. As an example, comparative studies suggest that the visual area MT in the upper temporal lobe of primates evolved from a visual area along the border of V2. A third and very important use of comparative studies is to provide another level of evaluation of theories developed from a particular species. Since the brains of different mammals are modifications of an ancestral plan, conclusions about brain organization in any given species should be consistent with those for other species, within the framework of evolutionary change. When current proposals for how visual cortex is organized in rats and humans are considered from a comparative point of view, key concepts are clearly challenged.
  Estelle

Author
       McKinney, Michael L.
Title
       Chapter
       Evolving behavioral complexity by extending development.
Source
       Parker, Sue Taylor (Ed); Langer, Jonas (Ed); et al. (2000). Biology,
brains, and behavior: The evolution of human development. School of
American Research advanced seminar series. (pp. 25-40). Santa Fe, NM, US; Santa Fe, NM, US:
School of American Research Press; School of American Research Press. xiii, 386 pp.
Abstract
       (from the chapter) Discusses recent work by paleontologists,
anthropologists, developmental biologists, neurobiologists, and
psychologists showing that the evolution  of hominid brain ontogeny has
been produced largely by the extension (prolonging) of brain growth and
development. In addition to evidence discussed elsewhere, the
author incorporates new evidence on the ultimate cause of our
extended growth in brain and cognition: predisplacement. The author
concludes with the point that a consistent pattern is produced of progressive
extension of brain development in a manner typical of peramorphoclines
throughout the history of life. The following topics are included: what are
juvenilization and overdevelopment? (relevance to human mental evolution;
overdevelopment = delays without rate reduction); our "overdeveloped" brain:
prolonging growth (high brain/body ratio; more neural complexity; more
neocortex and prefrontal cortex); our "overdeveloped" cognitive skills (evolution of
cognition, prolonged brain maturation as a cause of prolonged learning); mechanisms
of brain "overdevelopment"; does cognitive recapitulation occur?  (terminal extension,
not terminal addition; general brain and cognitive recapitulation); and hominid brain
evolution in the history of life. (PsycINFO Database Record
       (c) 2000 APA, all rights reserved)
  Arieti

Cantoni, Virginio. 1994. The Phylogenetic Evolution of the Visual System.
Chapter 1 of: Cantoni, Virginio. 1994. HUMAN AND MACHINE VISION: Analogies
and Divergencies. KLUWER/PLENUM H.
  Bas