Seminar announcement

[Gary Cottrell]

                                    SEMINAR

                                Cascading Maps:
                      Reorganization of Cortex in the Dog

                              Garrison W. Cottrell
                           Department of Dog Science
                    Southern California Condominium College


              "My dog is an old dog.  A major  difference  between
              owning  a  young dog and owning an old dog is walks.
              Young dog walks exercise the master; old  dog  walks
              exercise  the  master's  patience.  The major reason
              for this is _s_n_i_f_f_u_l_a _a_d _n_a_u_s_e_u_o_s_o, Latin  for  "this
              dog can't stop sniffing stuff".  Lest you think I am
              talking about something illegal, this dog just  will
              not  stop  sniffing  a  bush, a tree, or even a bare
              spot on the sidewalk.  You could  be  there  for  10
              minutes and he wouldn't be done yet."

                               --Professor Ebeneezer Huggenbotham


               The old dog sniffing problem (ODSP), or "Huggenbotham's
          tenth  problem",  has  provided  a  rich  source of data for
          recent advances in connectionist dog modeling.   Ever  since
          McDonnell & Pew's (McD & P) "Brain state in a Ball"[1] model
          of  the  dog  olfactory  bulb as an multi-state attractor, a
          debate  has  sprung  up  around  the  issue  of  whether   a
          connectionist net can actually exhibit dog-like behavior, or
          whether you needed to be a dog to possess dog-like  behavior
          (McDonnell  &  Pew,  1986;  Peepee, 1988; Pluckit & Walkman,
          1989).

          McD & P's model hypothesizes that since the brain  state  is
          in  a  ball, it can't ever get stuck in a corner, so it just
          wanders the surface of the sphere[2]. Thus the network never
          habituates to incoming signals.  Peepee's critique of McD  &
          P's  model  was  that since McD & P's model only contained 3
          units, it  could  never  represent  the  variety  of  smells
          available  to  old  dogs.   Pluckit  &  Walkman  showed that
          indeed, there  were  an  infinite  number  of  points  on  a
          hypersphere,  so  anything was representable.  Further, they
          showed that If one assumed the models had started with  many
          more  units  in  a  hypercube,  and lost them decrementally,
          converging on a 3-D sphere, that one could account for  many
          of  the  _d_e_g_r_a_d_a_t_i_o_n_a_l _a_s_p_e_c_t_s of the old dog's mind.  While
          these  models  accounted  for  many  of  the   psychological
          findings,  the  present  paper  seeks  to  integrate  recent
          neurophysiological findings into a new understanding of  old
          dog behavior.

          One of the  most  striking  phenomena  found  today  in  the
          cortical     map    literature   is   the   amazingly   fast
          reorganization of cortical maps.  In monkeys  whose  fingers
          have  been  severed,  the  somatosensory  map reorganizes to
          represent   the   other   fingers   more   than   before[3].
          Fortunately for dogs, they do not have fingers.  Fortunately
          for monkeys, it is also found that the map  will  reorganize
          without  vivisection.   If  the monkey is simply required to
          use a particular fingertip  for  some  task,  the  map  will
          allocate more space to that fingertip.  The surprising thing
          about this cortical reorganization is that it  is  1)  fast,
          happening over hours or days and 2)  present  in  adults[4].
          This  suggests  that  our  cortical  maps  may be constantly
          reorganizing.  Furthermore,  since  this  appears  to  be  a
          Hebbian-based reorganization, dependent upon activity, other
          maps connected to this one should also reorganize.  That is,
          reorganization  will  not be confined to somatosensory maps,
          but will _c_a_s_c_a_d_e to other areas.

          These observations suggest a new theory about representation
          in  the  elder  dog's  cortex.  As we all know, _s_m_e_l_l is the
          sense most associated with memory.   Since  input  from  the
          eyes  and  ears  degrades with age, the olfactory input will
          begin to dominate brain activity  in  the  older  dog.   The
          visual  and  auditory  maps  will  reorganize  to respond to
          smell.  They will not of course, _r_e_p_r_e_s_e_n_t smell,  but  will
          be  driven  more  by  smell than by eyes because of activity
          dependent remapping.  This will cause re-activation of vivid
          scenes associated with those smells.  Hence,  this  suggests
          that  the  reason  older  dogs  spend  an order of magnitude
          greater time than a younger dog sniffing the  same  spot  is
          that they are _r_e_m_i_n_i_s_c_i_n_g.

          ____________________
             [1]Unlike Anderson's model of human cortex  as  a  "Brain
          State  in  a Box", the states of the network are not allowed
          to extend outside of a _h_y_p_e_r_s_p_h_e_r_e.  This explains  why  hu-
          mans  are smarter than dogs: Humans can reach the _c_o_r_n_e_r_s of
          the hypercube.
             [2]Recently, more statistically based models have  argued
          that  the Kullback-Leibler information transmitted by an old
          nose was on the order of 1 bit per second (Chapel, 93), sug-
          gesting  the behavior is entirely a peripheral deficit.  Ex-
          perimental  1200  baud  "nodem"'s  are  being  implanted  in
          several dogs as a possible cure.
             [3]This line of research suggests  that  some  scientists
          did  not  pull  enough  legs  off  of spiders when they were
          younger.
             [4]This  also  suggests that modern American adult males,
          whose somatosensory maps overrepresent  certain  areas,  are
          capable of change.