*Noise in neurons is message-dependent*

*with M. Sigman, J-M. Alonso, L. Martinez, D. Chialvo
and M. Magnasco*

Go to the Neurobiology Page

*Noise-induced memory in extended excitable media*

*with D. Chialvo and M. Magnasco*

Go to the Neurobiology Page

We describe a form of memory exhibited by extended excitable systems driven by stochastic fluctuations. Under such conditions, the system self-organizes into a state characterized by power-law correlations thus retaining long-term memory of previous states. The exponents are robust and model-independent. We discuss novel implications of these results for the functioning of cortical neurons as well as for networks of neurons (Phys. Rev. E, 61(5), 5654-5658, May 2000).

(A): Hamming distance from initial sinusoidal pattern as a function of time. (B): Distance between two consecutives wavefronts as a function of noise.

*Negative Resistance in Brownian Transport*

*with Marcelo Magnasco*

*We prove that negative incremental resistance cannot occur on 1D
spaces like the circle or the line; we construct an explicit two-dimensional
model on the cylinder, and its collapse into a branched 1D backbone. We
derive an accurate numerical method for solving our 2D model, and discuss
the relevance of the model to biological ion channels. Physical Review
Letters 78 (11) 1968-1971 (1996).*

Plot of particle current as a function of the applied force

For repints, go to Macelo's Page

*Efficiency of DNA replication in the Polymerase
Chain Reaction*

*with Gustavo Stolovitzky*

*We present a detailed kinetic model for the Polymerase Chain Reaction,
and model the probability of replication in terms of the physical parameters
of the problem. Applying the theory of branching processes, we show the
existance of a new phenomenon affecting the probability distribution function
of the number of replicants: for small number of initial molecules, the
limiting behavior (with increasing number of cycles) of the pdf is represented
by a multi-modal funtion. Proceedings of
the National Academy of Sciences Volume 93, Number 23; Pages: 12947-12952,
November 12, 1996.*

Plot of the *pdf *of the number of molecules after 10 cycles for
one initial molecule

Also, go to Gustavo's Page