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C Taddei-Ferretti

Publications and source records attributed to C Taddei-Ferretti.

8 recordsLinked to original sources
PubMed1994

EXPLAN--a programming language for complex visual stimuli presentation.

Visual cognition research requires the flexible use of structured spatial patterns, characterized by various space and time parameters, which may be administered as visual stimuli. Dealing with this kind of study, we developed a special-purpose programming language and implemented a compiler to build executable programs. The language allows the presentation of stimuli, their space coordinates, persistency values, sequence, kinematic parameters, space-time proximity with other visual stimuli, determination of their modification according to external interaction, generation of subliminal stimuli, monitoring of different subject reactions, automatic reporting of stimulus presentation, and reaction monitoring. Such a language has been successfully utilized in a visual perception research.

Algorithms↗
PubMed1987

Modulation of Hydra attenuata rhythmic activity. IV. The mechanism responsible for rhythmic activity.

It has been hypothesized that the mechanism responsible for the rhythmic contraction-relaxation activity of Hydra attenuata is oscillatory. This nature is confirmed by the possibility of obtaining the suppression of overt behaviour by high frequency photic stimulation, which entrains the behaviour at a phase different from that giving rise to overt activity. Such a triggering mechanism should be structured as two different subsystems, mutually inhibiting. Also each one rebounds after the received inhibition in such a way that the active phase of each of them corresponds to the inhibited phase of the other one. This functional structure is argued from: 1. the existence of two triggering zones responsible for the contraction and relaxation phases; 2. the existence of a difference between the bioelectric potentials which reflect the activity of such triggering zones; 3. the opposite trend of these two bioelectric potentials at all phases in undisturbed conditions, and 4. the opposite direction of the variation of such bioelectric potentials as post-effects of either photic or electric stimulation, which follow the effects in the same direction undergone by the potentials themselves.

Animals↗
PubMed1976

Modulation of Hydra attenuata rhythmic activity: phase response curve.

We investigated the effect of photic stimulation on the frequency of Hydra attenuata column contractions. We used positive or negative abrupt light transitions, single or repetitive light or darkness pulses, and alternation of light and darkness periods. The main results are: (a) The frequency of the contraction pulse trains (CPTs) varies transiently in response to an abrupt variation of the light intensity. (b) CPTs in progress can be inhibited by different types of photic stimuli. (c) The response time to a single photic stimulus varies during the inter-CPT interval and depends also on the polarity of the stimulus. (d) The CPTs are entrainable with repetitive light stimulation of various frequencies. (e) Long-lasting variations of the frequency of CPTs occur after the end of a repetitive light stimulation. We suggest that the mechanism responsible for the rhythym of column contractions is quite similar to that on which other biological rhythmic phenomena are based.

Action Potentials↗
PubMed1975

Modulation of Hydra attenuata rhythmic activity. Photic stimulation.

We investigated in Hydra attenuata the possibility of altering more or less permanently and in different environmental conditions, the frequency of Contraction Pulse Trains (CPT's) associated with the rhythmic spontaneous contraction activity, by repetitive light stimuli of variable duration, frequency and amplitude. The CPT's activity of various pieces of Hydra has been also investigated in indisturbed conditions and under stimulation. The following observations have been performed. 1. A transient effect, consisting of an increase or a decrease of CPT's frequency, occurs respectively after an abrupt decrease or increase of the light level. 2. If Hydra is stimulated by repetitive light pulses of 0.5-10 sec duration, at a frequency different from the CPT's average one, the CPT's frequency modifies; if the stimulation frequency is included in a range not too much up or below that of CPT's the new CPT's frequency equals exactly that of stimulation; close to this range the CPT's frequency is a multiple or submultiple of that of stimulation. 3. No habituation to such repetitive stimulation was found. 4. The phase relation between CPT's at the new frequency and light stimuli is a function of the difference between CPT's and stimulation frequencies. 5. Stimulation with repetition of light and darkness periods of some minutes duration induces activity only or mainly during darkness. 6. Modification of CPT's frequency by means of repetitive light stimulation [of the type mentioned either in 2) or 5)] has been observed also with hypostomal preparations. 7. With cessation of the light stimulation, the new CPT's frequency of the whole animal lasts in darkness for a time (10-85 min) that is about 5-10 times longer than that necessary to obtain CPT's syncronization with stimulation. 8. The influence of the light intensity level on transient CPT's frequency variation (see 1), CPT's inhibition and stimulation, promptness of entrainment, range of entrainability, phase relation between entrained CPT's and stimuli, retention time of entrained rhythm has been examined, together with the influence of the reversal of polarity of light transitions on CPT's inhibition and entrainment.

Animals↗
PubMedDate not supplied

Modulation of membrane potential in algal cells by temperature gradients. A thermodynamic approach.

The aim of the present study is to ascertain whether transmembrane temperature gradients couple with transport of electric charge in living cells of Valonia utricularis and eventually measure the thermodynamic coupling coefficient (s). Simple experimental procedures are described that allow generation of temperature gradients of predetermined sense and intensity across the cell membrane. Simultaneous measurement of the potential difference is ensured by standard electrophysiological methods. The mathematical expressions that allow quantitative treatment of experimental results are indicated in the article and are based on standard nonequilibrium thermodynamic and electrophysiological formalism. The value of the coupling coefficient between temperature gradient and flow of electric charge is indicated and concisely discussed in terms of possible mechanisms of ionic membrane transport.

Biological Transport↗